Développement d’une approche intégrée pour la gestion de l’eau en production de canneberges

Thèse

Vincent Pelletier

Doctorat en sols et environnement Philosophiae doctor (Ph. D.)

Québec, Canada

© Vincent Pelletier, 2016

Développement d’une approche intégrée pour la gestion de l’eau en production de canneberges

Thèse

Vincent Pelletier

Sous la direction de :

Jacques Gallichand, directeur de recherche

Steeve Pepin, codirecteur de recherche

iii

Résumé

Dans un contexte évolutif où les changements climatiques entraîneront une augmentation du

nombre d’événements climatiques extrêmes, la gestion de l’eau devra être optimisée afin d’éviter

l’impact des stress environnementaux sur le rendement agronomique des cultures. Bien que les

seuils où surviennent ces stress soient connus pour la majorité des espèces agricoles, ils demeurent

pour la plupart inconnus pour la canneberge. Leur détermination est donc un prérequis à

l’établissement d’une gestion de l’eau efficace et durable. Conséquemment, des expérimentations

au champ et en cabinet de croissance ont été réalisées afin d’étudier l’impact des principaux stress

abiotiques sur la canneberge et de proposer des stratégies innovatrices menant à une approche

intégrée de la gestion de l’eau dans cette culture. En maintenant la nappe phréatique à une

profondeur de 60 cm sous la surface du sol, les rendements ont été maximisés et l’application d’eau

par aspersion a été minimisée. Cependant, les canneberges sont très sensibles aux problèmes de

drainage. En effet, lors de deux études de cas, une diminution de rendement de 25 à 39% a été

mesurée lorsque le système de drainage n’était pas entièrement fonctionnel. Puisque contrôler la

nappe peut ralentir le drainage et entraîner une diminution de l’aération dans la rhizosphère suite à

une précipitation, une expérience en cabinet de croissance a été réalisée afin de déterminer la

tolérance de la canneberge aux conditions hypoxiques. Les résultats ont démontré une diminution

de 28% de la photosynthèse après 24 heures en conditions saturées. Le système de drainage doit

donc permettre d’évacuer rapidement les surplus d’eau afin d’éviter de telles conditions. Avec le

contrôle de nappe, l’air entourant le feuillage est plus chaud et plus sec en comparaison avec

l’irrigation par aspersion, ce qui peut entraîner davantage d’épisodes de stress thermique. Une

expérimentation en cabinet de croissance a permis d’identifier qu’en comparaison à une température

optimale de 29 °C, la photosynthèse diminue de 11% à 33 °C et de 22% à 37 °C. Refroidir le

feuillage pendant 20 minutes lorsque la température y atteint 33 °C s’est alors avéré bénéfique pour

éviter le stress thermique. En intégrant ces nouveaux paramètres de gestion de l’eau, les producteurs

de canneberges pourront maximiser le rendement agronomique de leur culture et en réduire son

impact environnemental.

iv

Abstract

In an evolving context where climate change will cause an increase in extreme weather events,

agricultural water management will have to be optimized in order to limit the impact of

environmental stresses on crop yields. Although critical thresholds where these stresses occur have

been established for several plant species, little is known about these relationships in cranberry

production. Hence, the determination of these thresholds is then a prerequisite for developing of a

sustainable water management. Consequently, field and growth cabinet experiments were carried

out to study the impact of the main abiotic stresses on cranberries and to propose innovating

strategies leading to a holistic approach for water management. By controlling the water table at 60

cm depth below soil surface, yields were maximized and overhead irrigation was minimized.

However, cranberries are very sensitive to poor drainage conditions. In two case studies, yield

losses of 25 and 39% were associated to drainage problems. Because controlling water table depth

may slow down drainage rate and lead to oxygen deficiency in the rhizosphere following rainfall, a

growth cabinet experiment was needed for determining cranberry tolerance to hypoxic conditions.

Because the results showed that photosynthesis declined by 28% after the 1st day of waterlogging,

drainage systems should be fully efficient in avoiding such conditions. Managing water table depth

leads to drier canopy conditions than sprinkler irrigation, and thus may increase the vapor pressure

deficit near the foliage and the risk of heat stress. Under controlled conditions, the optimal

temperature range for carbon assimilation was between 25 and 29 °C, with photosynthesis declining

by 11% at 33 °C and by 22% at 37 °C. Under controlled environmental conditions, cooling the

vines for 20 minutes when temperature reaches 33 °C was beneficial to limit heat stress and was

able to reduce photosynthetic midday depression. By integrating these new parameters and

strategies to water management, cranberry growers will maximize crop yields while reducing the

crop environmental impact.

v

Table des matières

Résumé .............................................................................................................................................. iii Abstract ............................................................................................................................................. iv Table des matières ............................................................................................................................. v Liste des tableaux ............................................................................................................................ vii Liste des figures .............................................................................................................................. viii Liste des abréviations ........................................................................................................................ x Remerciements ................................................................................................................................ xii Avant-Propos .................................................................................................................................. xiii  CHAPITRE 1 Introduction générale ........................................................................................................................ 1 

1.1.  Mise en contexte ....................................................................................................................... 2 1.2.  La canneberge et sa production ................................................................................................. 3 1.3.  Stress abiotiques environnementaux ......................................................................................... 5 1.4.  Gestion de l’eau ........................................................................................................................ 6 

1.4.1. Irrigation par aspersion ...................................................................................................... 6 1.4.2. Irrigation souterraine ......................................................................................................... 7 1.4.3. Drainage ............................................................................................................................ 8 1.4.4. Irrigation de refroidissement ............................................................................................. 8 

1.5.  Problématique ........................................................................................................................... 9 1.6.  Objectifs .................................................................................................................................. 10 

CHAPITRE 2   Water Table Control for Increasing Yields and Water Savings in Cranberry Production ..... 12 

2.1.  Introduction ............................................................................................................................. 15 2.2.  Experimental section ............................................................................................................... 17 2.3.  Results and discussion ............................................................................................................ 21 

2.3.1. First criteria: Increasing yield without decreasing fruit quality ...................................... 21 2.3.2. Second criteria: Minimal use of sprinkler irrigation ....................................................... 28 2.3.3. Third criteria: Fast drainage ............................................................................................ 30 

2.4.  Conclusion .............................................................................................................................. 30 2.5.  Acknowledgements ................................................................................................................. 32 2.6.  References ............................................................................................................................... 33 

CHAPITRE 3   Cranberry Gas Exchange under Short-term Hypoxic Soil Conditions ...................................... 36 

3.1.  Introduction ............................................................................................................................. 39 3.2.  Materials and Methods ............................................................................................................ 40 3.3.  Results ..................................................................................................................................... 42 3.4.  Discussion ............................................................................................................................... 45 3.5.  Conclusion .............................................................................................................................. 47 3.6.  Acknowledgements ................................................................................................................. 47 3.7.  References ............................................................................................................................... 48 

CHAPITRE 4   Impact of Drainage Problems on Cranberry Yield: Two Case Studies ..................................... 50 

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4.1.  Introduction ............................................................................................................................. 53 4.2.  Case study #1 .......................................................................................................................... 53 4.3.  Case study #2 .......................................................................................................................... 55 4.4.  Practical implications .............................................................................................................. 56 4.5.  Conclusion .............................................................................................................................. 57 4.6.  Acknowledgements ................................................................................................................. 57 4.7.  References ............................................................................................................................... 58 

CHAPITRE 5   Reducing Cranberries Heat Stress and Midday Depression with Evaporative Cooling .......... 59 

5.1.  Introduction ............................................................................................................................. 62 5.2.  Materials and Methods ............................................................................................................ 63 

5.2.1. Determination of the critical temperature threshold ........................................................ 63 5.2.2. Effect of environmental variables and sprinkler irrigation on cooling efficiency in field conditions .................................................................................................................................. 65 5.2.3. Gas exchange responses to cooling treatments ............................................................... 66 

5.3.  Results ..................................................................................................................................... 68 5.3.1. Determination of the critical temperature threshold ........................................................ 68 5.3.2. Effect of environmental variables and sprinkler irrigation on cooling efficiency in field conditions .................................................................................................................................. 68 5.3.3. Gas exchange responses to cooling treatments ............................................................... 71 

5.4.  Discussion ............................................................................................................................... 73 5.4.1. Determination of the critical temperature threshold ........................................................ 73 5.4.2. Effect of environmental variables and sprinkler irrigation on cooling efficiency in field conditions .................................................................................................................................. 75 5.4.3. Gas exchange responses to cooling treatments ............................................................... 75 

5.5.  Conclusion .............................................................................................................................. 76 5.6.  Acknowledgements ................................................................................................................. 77 5.7.  References ............................................................................................................................... 78 

CHAPITRE 6   Proposing Field Guidelines for Cranberry Water Management: Integrating latest discoveries ……………........................................................................................................................................81 

6.1.  Introduction ............................................................................................................................. 84 6.2.  Water management strategies ................................................................................................. 86 

6.2.1. Avoiding water stress ...................................................................................................... 86 6.2.2. Avoiding heat stress ........................................................................................................ 89 6.2.3. Avoiding frost damage .................................................................................................... 90 6.2.4. Avoiding hypoxic conditions .......................................................................................... 90 

6.3.  Conclusions and recommendations ......................................................................................... 91 6.4.  Acknowledgements ................................................................................................................. 93 6.5.  References ............................................................................................................................... 94 

CHAPITRE 7   Conclusion générale et perspectives futures ................................................................................. 97 

7.1.  Conclusion générale ................................................................................................................ 98 7.2.  Perspectives futures .............................................................................................................. 100 

Bibliographie ................................................................................................................................. 101 

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Liste des tableaux

CHAPITRE 2

Table 2.1. Characteristics of the experimental sites. ........................................................................ 17 

Table 2.2. Monthly climatic data at the experimental site in St-Louis-de-Blandford, Québec, Canada and long term averages from a public weather station located 8 km away from Site A and 5 km away from sites B and C. ............................................................................................................ 18 

Table 2.3. Irrigation water applied at each site for 2013-2014 and weekly averaged water table depth (WTD). .................................................................................................................................... 29 

CHAPITRE 5

Table 5.1. Photosynthesis of cranberry fruiting uprights (n=6 to 9 per treatment) averaged over a 5 h period (11:30-16:30) on Day 0 (An-D0), Day 1 (An-D1), and the difference between Day 1 and Day 0 (ΔAn) for each cooling treatment (C0: control, C1: one event, and C3: three events) and soil water tension (SWT) treatment (T4: 4.0 kPa, T7: 7.5 kPa, and T15: 15.0 kPa) ......................................... 71 

Table 5.2. Effect of cooling treatments (C0: control, C1: one event, and C3: three events) on photosynthetic midday depression (An-loss) of cranberry fruiting uprights, calculated as the difference between the maximum rate of photosynthesis in the morning and that measured at 15:00 h (averaged over 15 minutes) ............................................................................................................ 73 

Table 5.3. Number of days on a yearly basis (1990-2014) where the daily maximum air temperature (TA-max) reached values from 25 to 37°C for the seven most productive cranberry-growing regions in North America ................................................................................................................................... 74 

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Liste des figures

CHAPITRE 1

Figure 1.1. Statistiques de production des sept plus importantes régions productrices de canneberges pour la période 1990-2014 .............................................................................................. 3 

CHAPITRE 2

Figure 2.1. The experimental sites. .................................................................................................. 17 

Figure 2.2. (a) Volumetric soil water content and (b) hydraulic conductivity in relation with soil water tension.. ................................................................................................................................... 19 

Figure 2.3. Boundary line approach of (a) yield and (b) number of berries in relation with the averaged water table depth (WTD) during the growing season of 2014 ........................................... 21 

Figure 2.4. Filled contour of weekly average water table depth for the three sites between June and September in 2013 and 2014 ............................................................................................................. 23 

Figure 2.5. Crop yield at the three sites in 2014.. ............................................................................. 26 

Figure 2.6. Yield components in relation with the averaged water table depth (WTD) during the growing season. (a) Percentage of fruit set per flower; (b) Number of berries per fruiting upright; (c) Berry weight (d) Number of fruiting uprights per ring of 182 cm2.. ................................................. 27 

Figure 2.7. Yield quality parameters in relation with the averaged water table depth (WTD) during the growing season. (a): Total soluble solids (TSS); (b) Titratable Acidity (TA); (c) Ratio of TSS on TA; (d) Total Anthocyanin (TAcy).. ................................................................................................. 28 

Figure 2.8. Soil Water Tension and manual readings of Water Table Depth at each site for 2013 and 2014. ........................................................................................................................................... 31 

Figure 2.9. Time required for the soil water tension (SWT) to return to a value of 3.0 kPa (WTD = 40 cm) after a major rainfall event as a function of the SWT just before the rainfall event. ............ 32 

Figure 2.10. Soil water tension (SWT) for a rainfall of 33 mm for different values of SWT just before the rainfall .............................................................................................................................. 32 

CHAPITRE 3

Figure 3.1. Changes in (a) photosynthesis (Pn) and (b) stomatal conductance (gs) as a function of the number of days with saturated soil conditions at the stage of bud elongation, flowering, and fruit development. ..................................................................................................................................... 43 

Figure 3.2. Photosynthesis as a function of the number of days after drainage at the stage of bud elongation, flowering, and fruit development for treatment with (a) 1, (b) 2, (c) 3, and (d) 5 consecutive day of soil saturation. .................................................................................................... 44 

CHAPITRE 4

Figure 4.1. The swollen masses found at the drain outlet after pumping water at low operating pressure (300 kPa) in drain pipes for washing. ................................................................................. 54 

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Figure 4.2. Monitoring the development of cranberries growing over drain pipes clogged with swollen masses from June 7 to August 17 2012 ............................................................................... 54 

Figure 4.3. Temporal variations of soil water potential values after the end of rainfall (time=0) until it return to the target of -3 kPa in both section (West vs East) of a cranberry bed. In a) rainfall was 29 mm; the depth of the drainage outlet was problematic at the West extremity of the bed and in b) rainfall was 26 mm; the drainage outlet problem was corrected. ...................................................... 56 

CHAPITRE 5

Figure 5.1. Layout of the six cranberry beds used in the experiment to identify the effects of environmental variables and sprinkler irrigation on cooling efficiency in field conditions. ............. 66 

Figure 5.2. Time course of cranberry leaf temperature (TL) during two days of gas exchange measurements (D0 and D1) for three cooling treatments .................................................................. 67 

Figure 5.3. Standardized (a) photosynthesis (An), (b) stomatal conductance (gs), and (c) transpiration (Tr) in relation to leaf temperature (TL) and soil water tension.. Values corresponding to the maximum for each combination of leaves and soil water tension are presented in (d). .......... 69 

Figure 5.4. Efficiency of evaporative cooling in relation to the difference in temperature of cranberry foliage (ΔTF) immediately before and after the sprinkler irrigation. Data are from field experiments where irrigation was initiated when TF reached 33 °C. ................................................ 70 

Figure 5.5. Difference in temperature of cranberry foliage (ΔTF) due to evaporative cooling as a function of environmental conditions just before irrigation. (a) Vapor pressure deficit in the canopy foliage (VPDF), (b) relative humidity in the canopy foliage (RHF), (c) air temperature at the weather station (TA,2-m), (d) wind speed, (e) solar radiation (Rad), and (f) relative humidity at the weather station (RHA,2-m). ............................................................................................................................... 70 

Figure 5.6. (a) Temperature and (b) relative humidity in the canopy foliage of non-irrigated and irrigation treatments and at the weather station between 08:00-20:00 h on June 27th 2014. ............. 71 

Figure 5.7. (a) Midday depression of photosynthesis (An) observed at ~11:00 h on Day 1 when cranberry leaf temperature (TL) in the LI-6400 chamber was increased from 21 °C to 33 °C whereas on Day 0, TL was kept constant at 27°C from 11:00 to 17:00 h. (b) Absence of a midday depression. Here, there was no cooling episode and soil water tension was 4.0 kPa. ....................... 72 

CHAPITRE 6

Figure 6.1. Statistics of the cranberry production for the seven major producing area (BC: British Columbia, MA: Massachusetts, NJ: New Jersey, OR: Oregon, QC: Québec, WA: Washington, WI: Wisconsin). a) Yield, b) Harvested area, and c) Volume. ................................................................. 84 

Figure 6.2. Empirical relationship between soil water conditions and cranberry yields / photosynthesis. From the general relationship, many questions remained unanswered on the optimum maintain of aeration and water flux. .................................................................................. 86 

Figure 6.3. Guidelines for complete irrigation management approach using new technologies in cranberry production. ........................................................................................................................ 92 

x

Liste des abréviations

Symbole Anglais Français Unité

An et Pn Photosynthesis Photosynthèse µmol m-2 s-1

Ci Intermolecular CO2 concentration Concentration intercellulaire du CO2 µmol mol-1

E et Tr Leaf transpiration Transpiration foliaire mmol m-2 s-1

gs Stomatal conductance Conductance stomatique mol m-2 s-1

GDD Growing degree days (5 °C base) Degré-jour de croissance (Base 5 °C) -

PPFD Photosynthesis photon flux density Densité de flux de photons pour la photosynthèse

µmol m-2 s-1

RHF Relative humidity in the canopy Humidité relative dans la canopée %

RHA,2-m Relative humidity at 2-m height Humidité relative à 2-m d’élévation %

SWT Soil water tension Tension de l’eau dans le sol kPa

SWP Soil water potential Potentiel matriciel de l’eau dans le sol kPa

TL Leaf temperature Température de la surface de la feuille °C

TF Temperature in the canopy Température dans la canopée °C

TA,2-m Temperature at 2-m height Température à 2-m d’élévation °C

VPDl Leaf-to-air vapor pressure deficit Gradient de pression de vapeur d’eau entre la feuille et l’air

kPa

VPDF Vapor pressure deficit near the foliage

Gradient de pression de vapeur près du feuillage

kPa

WTD Water table depth Profondeur de la nappe phréatique cm

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À mon père, qui n’aura pu voir l’aboutissement

de tous ces travaux.

xii

Remerciements

Cette thèse n’aurait pu voir le jour sans l’encadrement, l’aide et le soutien de plusieurs personnes.

Tout d’abord, j’aimerais remercier mon directeur de recherche, Jacques Gallichand, pour sa grande

disponibilité, sa rigueur, ses valeureux conseils et pour m’avoir aidé à garder une ligne directrice

dans tous mes travaux. Merci à mon co-directeur, Steeve Pepin, pour avoir pris le temps de

répondre à mes 1001 questions (bien souvent à l'improviste et dans un cadre de porte!) sur la

physiologie végétale afin de palier à mes lacunes dans ce domaine. Sa généreuse aide apportée lors

du montage des expériences en cabinet de croissance, bien souvent en urgence et/ou tard en fin de

journée, a largement contribué aux succès de ces travaux.

Merci à Jean Caron de m’avoir soutenu depuis le début de mes études graduées et pour les

nombreuses conversations sur la physique du sol, l’irrigation, l’agriculture, la recherche, la science,

la société et j’en passe! Merci à Silvio Gumiere, non seulement pour les pauses caféinées, mais

aussi pour son aide apportée lors de chaque étape de mon doctorat.

J’aimerais remercier spécialement Jonathan Lafond pour ses divertissants jeux de mots! Tout

comme Benjamin Parys, j’aimerais également le remercier pour l’aide apportée à l’organisation des

journées de champ et des analyses en laboratoire. Merci à Jean-Philippe Gagné, Guillaume Gagnon,

Jade Blais, Alexandra Déry et Christian Gagnon ainsi qu’aux nombreux autres étudiants de premier

cycle pour leur aide lors de la mise en place des expériences et pour l’échantillonnage des

rendements. Sans leur précieuse collaboration, je n’aurais pu mener à terme mes expérimentations.

Merci également à mes collègues et amis aux études graduées pour la camaraderie universitaire

entretenue pendant toutes ces années. Merci à Claude-Émilie Canuel pour ses commentaires

bénéfiques lors du processus de révision.

Ce projet n’aurait pu avoir lieu sans la participation, l’aide et le soutien de plusieurs entreprises et

organismes partenaires au projet. Un merci spécial aux gens de Hortau, Canneberges Bieler, Nature

Canneberge, Mont Atoca, du CRSNG et du FQRNT.

La famille, la belle-famille et les amis jouent également un rôle de premier plan de par leurs

encouragements et leur support. Merci à tout mon entourage de m’avoir épaulé.

Finalement, mes remerciements les plus amoureux vont à ma fiancée, Marie-Pier, pour son

incroyable patience. Je lui avais promis qu’il me restait une seule année d’études lorsque nous nous

sommes rencontrés… il y a de cela six ans!

xiii

Avant-Propos

Le chapitre 1 de cette thèse est une introduction générale évoquant la mise en contexte ainsi que la

problématique soulevée ayant menée au développement d’une hypothèse principale et des objectifs

permettant de la soutenir. Nous avons répondu à ces objectifs et ils ont été développés sous la forme

d’articles scientifiques publiés ou acceptés par un comité de révision et composent les chapitres 2 à

5 de la thèse. Le chapitre 6 est une synthèse de la contribution des précédents chapitres à

l’avancement de la connaissance ainsi que les implications pratiques engendrées par ces derniers.

Ce chapitre constitue une partie de l’article cité ci-dessous. J’ai écrit la première version des

chapitres 2 à 6, laquelle a été révisée et améliorée par chacun des co-auteurs. Chacun des co-auteurs

a également participé à la planification des expériences et à l’interprétation des résultats. Le

chapitre 7 intègre dans une conclusion générale les principaux résultats obtenus et se termine sur les

perspectives futures rattachés à ces travaux. Les références pour les chapitres 2 à 6 sont les

suivantes:

CHAPITRE 2: Publié le 7 août 2015

Pelletier, V., Gallichand, J., Gumiere, S. Pepin, S., Caron, J. 2015. Water table control for

increasing yield and saving water in cranberry production. Sustainability. 7:10602-10619.

CHAPITRE 3: Accepté le 2 mai 2016

Pelletier, V., Pepin, S., Laurent, T., Gallichand, J., Caron, J. Cranberry gas exchange under

short-term hypoxic soil conditions. HortScience. (accepted)

CHAPITRE 4: Publié le 7 avril 2016

Pelletier, V., Gallichand, J., Gumiere, S., Caron, J. Impact of drainage problems on cranberry

yield: Two case studies. Can. J. Soil Sci. 10.1139/CJSS-2015-0132.

CHAPITRE 5: Publié le 13 décembre 2015

Pelletier, V., Pepin, S., Gallichand, J., Caron, J. Reducing cranberry heat stress and midday

depression with evaporative cooling. Sci. Hortic. 198:445-453.

CHAPITRE 6: Sera prochainement soumis à Can. J. Soil Sci.

Pelletier, V., Gallichand, J., Gumiere, S., Pepin, S., Bland, W.L., Kennedy, C., Caron, J.

Proposing Field Guidelines for Cranberry Water Management: Integrating latest discoveries.

xiv

Les résultats obtenus dans les précédents chapitres ont également été présentés lors des congrès

scientifiques nationaux et internationaux suivants :

PRÉSENTATIONS ORALES :

Pelletier, V., Gallichand, J., Pepin, S., Gumiere, S., Caron, J. Increasing Cranberry Yield by Improving Irrigation and Drainage. Présentée lors de l’Atlantic Cranberry Management Course le 1er avril 2016 à Charlottetown (Île-du-Prince-Édouard, Canada).

Pelletier, V., Gallichand, J., Pepin, S., Gumiere, S., Caron, J. L’importance de la conception des systèmes de drainage pour éviter les conséquences négatives reliées à l’excès d’eau dans le sol. Présentée lors d’INPACQ Canneberges le 28 janvier 2016 à Victoriaville (Québec, Canada).

Pelletier, V., Gallichand, J., Gumiere, S., Pepin, S., Caron, J. Water table control for increasing yield and saving water in cranberry production. Présentée lors du North American Cranberry Researcher and Extension Workers (NACREW) Conference le 25 août 2015 à Bandon (Oregon, USA).

Pelletier, V., Gallichand, J., Gumiere, S., Pepin, S., Caron, J. Controlling water table depth for a sustainable cranberry production. Présentée lors du congrès conjoint de Commission 2.5 of the International Union of Soil Science, de la Société Canadienne de Science du Sol (SCSS) et de l’Association québécoise des spécialistes en sciences du sol (AQSSS) le 6 juillet 2015 à Montréal (Québec, Canada).

AFFICHES:

Pelletier, V., Pepin, S., Bonin, S., Gallichand, J., Caron, J. Environmental stresses in cranberry production: Critical thresholds and physiological effects. Présentée lors du North American Cranberry Researcher and Extension Workers (NACREW) Conference du 24 au 26 août 2015 à Bandon (Oregon, USA).

Pelletier, V., Pepin, S., Bonin, S., Gallichand, J., Caron, J. Environmental stresses in cranberry production: Critical thresholds and physiological effects. Présentée lors de l’American Society of Horticultural Science (ASHS) Annual Conference du 4 au 7 août 2015 à la Nouvelle-Orléans (Louisiane, USA).

Pelletier, V., Pepin, S., Laurent, T.J., Gallichand, J., Caron, J. Short-term flooding effects on gas exchange and plant productivity of cranberries. Présentée lors de l’Annual meeting of the Soil Science Society of America (SSSA) du 2 au 5 novembre 2014 à Longbeach (Californie, USA).

Pelletier, V., Pepin, S., Gallichand, J., Caron, J. Plan décisionnel de gestion de l’eau axé sur le contrôle de nappe et basé sur la quantification des besoins en eau en production de canneberges. Présentée lors du 28e colloque de l’Association Québécoise de Spécialistes en Sciences du Sol (AQSSS) du 26 au 29 mai 2014 à Victoriaville (Qc).

Pelletier, V., Gallichand, J., Pepin, S., Caron, J. Optimal water table depth in cranberry subirrigation. Présentée lors de l’American Society of Agricultural and Biological Engineers (ASABE) du 13 au 16 juillet 2014 à Montréal (Québec, Canada).

1

CHAPITRE 1 Introduction générale

2

1.1. Mise en contexte

Les origines de l’industrie de la canneberge remontent aux premières années du 19e siècle au

Massachusetts (Eck, 1990). Les états américains du nord-est de l’Amérique du Nord, où la

canneberge y pousse naturellement dans les milieux humides, ont dominé le marché jusqu’au milieu

des années 1990 lorsque le Wisconsin est devenu la principale région productrice (Figure 1.1a). À

cette époque, le Québec ne comptait que trois producteurs, mais en 2014, au moment où il est

devenu le deuxième plus important producteur mondial (Figure 1.1c), 84 producteurs y cultivaient

une superficie cumulative de 3450 hectares (Figure 1.1b). Lors des 10 dernières années, le volume

de canneberges récoltées au Québec a augmenté de 338% alors que le rendement y a augmenté en

moyenne de 7% par année. Globalement, l’industrie a produit en moyenne 21 milliers de tonnes de

fruits de plus à chaque année pendant la période 2005-2014, approximativement le double de la

période 1995-2004 avec une augmentation moyenne de 12 milliers de tonnes de fruits par année

(APCQ, 2015).

L’industrie de la canneberge est donc en pleine expansion et afin de demeurer compétitifs, les

producteurs devront miser sur une augmentation des rendements et sur la production de fruits de

qualité. En effet, afin de stimuler la vente de produits à base de canneberges, l’industrie cherche à

offrir des produits possédant une concentration élevée en anthocyanines et en sucres naturels, sans

toutefois en sacrifier le goût acidulé (Nolte, 2015).

Dans un contexte évolutif où les changements climatiques entraineront l’accroissement de certains

stress environnementaux (e.g., hydrique, thermique, hypoxique) causée par l’augmentation de la

température et du nombre d’événements climatiques extrêmes (IPCC, 2013), les pratiques culturales

telles que l’irrigation et le drainage devront être optimisées afin d’améliorer l’efficacité de

l’utilisation de l’eau. Par ailleurs, le resserrement de la réglementation sur la qualité des eaux

rejetées dans l’environnement (Kennedy et al., 2015; DeMoranville et al., 2015) et sur les résidus de

pesticides contenus dans les fruits (Wilson, 2015) obligent les producteurs à modifier leurs

pratiques culturales afin de réduire l’impact environnemental de la production de canneberges. La

présente étude s’inscrit donc dans un contexte où les producteurs font face à une nouvelle contrainte

majeure: augmenter le rendement et la qualité des fruits tout en diminuant l’impact sur

l’environnement.

3

Figure 1.1. Statistiques de production des sept plus importantes régions productrices de canneberges pour la période 1990-2014: Colombie-Britannique (BC), Massachusetts (MA), New Jersey (NJ), Oregon (OR), Québec (QC), Washington (WA) et Wisconsin (WI). (a) Rendement, (b) Superficie et (c) Volume de fruits récoltés. Source : NASS (2015), APCQ (2015) et BCCMC (2015).

1.2. La canneberge et sa production

D’un point de vue botanique, la canneberge fait partie du genre Vaccinium de la famille Ericaceae.

Ce genre regroupe plus de 450 espèces dont font partie les airelles, les bleuets et les myrtilles et se

retrouve à l’état sauvage dans les sols acides tels que les marais et les tourbières. L’espèce cultivée

de la canneberge, macrocarpon, provient du nord-est de l’Amérique du Nord (Eck, 1990). En

production, Vaccinium macrocarpon Ait. recouvre le sol grâce aux stolons sur lesquels poussent des

tiges verticales de 5 à 20 cm avec un bourgeon à leur extrémité (Sandler et DeMoranville, 2008).

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4

L’année suivante, un bourgeon sur deux se développera en tige fructifère (Strik et coll., 1991) sur

laquelle se formeront en moyenne quatre fleurs, dont environ la moitié se transformera en fruits

(Pelletier et coll., 2015). Les racines, très fines, fibreuses et ne possédant aucun poil absorbant,

peuvent atteindre entre 7 et 15 cm de profondeur (Sandler et DeMoranville, 2008) tandis que les

feuilles, vert foncé pendant la saison de croissance et rougeâtre lors de la dormance, mesurent entre

8 et 13 mm (Binet et coll., 1997). Afin d’assurer une croissance normale, une période de dormance

minimale de 2500 heures est requise (Eady et Eaton, 1972).

Lors de l’aménagement d’une ferme de canneberges, la surface des champs est nivelée afin de

faciliter l’inondation lors de la récolte. Lorsque la pente naturelle du terrain devient trop importante,

un deuxième niveau de champs est créé. Un terrain avec une pente inférieure à 1% est donc

recommandé pour éviter les coûts reliés au transport de nouveau matériel pour le nivellement (Binet

et coll., 1997). Des digues d’environ un mètre de haut sont aménagées entre chaque champ à partir

des débris de végétation et de la couche organique de surface retirés lors du défrichement et du

dessouchage du site. Ces digues permettent la circulation de la machinerie et la création de bassins

pour l’inondation des champs lors de la récolte. Les systèmes de drainage et d’irrigation sont alors

installés et les canneberges peuvent être plantées. Après la deuxième ou la troisième année, les

champs produisent leur première récolte et avec un entretien adéquat, ils produiront pendant plus

d’un siècle (Eck, 1990).

La protection contre le gel à l’aide des systèmes d’irrigation par aspersion est essentielle à la survie

des organes reproducteurs. L’ajout d’eau entraîne la formation de glace sur la surface des plantes,

ce qui dégage une chaleur permettant aux plantes d’être protégées jusqu’à une température

atteignant -10 °C (Binet et coll., 1997). Lorsque la densité du feuillage est trop élevée et que les

tiges végétatives sont jugées trop longues, les plantes peuvent être taillées mécaniquement.

L’éclaircissement de la canopée permet d’augmenter le taux de photosynthèse des tiges fructifères

et de briser la dominance apicale afin de favoriser la croissance de nouveaux bourgeons latéraux

(Suhayda et coll. 2009). L’ajout de ruches d’abeilles et de bourdons, généralement dans les derniers

jours de juin et dans les premiers jours de juillet, est essentiel pour assurer la pollinisation des fleurs

(Cane et Schiffhauer, 2003; Gaines-Day et Gratton, 2015). S’ensuit alors l’application de fertilisants

et de pesticides à l’aide de la machinerie équipée de rampes d’aspersion circulant entre les champs.

L’inondation des champs est utilisée dans le but de faciliter la récolte des fruits vers la fin

septembre et le début octobre. Avec cette méthode, les fruits sont détachés des plantes

mécaniquement, flottent à la surface de l’eau et sont rassemblés vers une extrémité du champ à

l’aide de barrages flottants pour être aspirés dans un convoyeur et dirigés vers la benne d’un camion

5

(Sandler et al. 2004). Un système de circulation de l’eau sur la ferme permet d’acheminer l’eau

utilisée d’un champ inondé vers un champ à inonder. Le même système est utilisé pendant la saison

de croissance pour évacuer les excès d’eau par drainage souterrain et pour acheminer l’eau vers les

systèmes d’irrigation. Une gestion efficace de l’eau est primordiale pour éviter que la plante ne

subisse des conditions de stress abiotiques pouvant entraîner une diminution des rendements.

1.3. Stress abiotiques environnementaux

La pression exercée sur les végétaux par des conditions environnementales défavorables impose des

contraintes, tel que les stress hydriques, hypoxiques et thermiques pouvant affecter le

développement normal des plantes. Les plantes doivent être en mesure de prélever l’eau dans le sol

par leur système racinaire et le CO2 de l’atmosphère par leurs stomates pour limiter l’effet de ces

contraintes.

L’eau est essentielle à la survie des plantes et leur habileté à tolérer le stress hydrique est cruciale.

Lorsque le flux d’eau dans le sol devient limitant pour le prélèvement racinaire, la fermeture des

stomates est l’une des premières réactions menant à une réduction du taux de photosynthèse (Anjum

et coll., 2011). Afin d’éviter une perte substantielle de la turgescence des feuilles et des dommages

irréversibles aux systèmes membranaires internes, certaines plantes ont la capacité de réguler les

pertes en eau par la fermeture partielle de leurs stomates (Zhang et coll., 2006). Lorsque l’expansion

cellulaire est altérée, la croissance de la plante entière est affectée et le rendement agronomique peut

diminuer (Arve et coll., 2011).

Suite à une forte précipitation ou à un excès d’irrigation, le surplus d’eau dans le sol produit des

conditions hypoxiques (Lia et Lin, 2001) qui entraînent une diminution de l’absorption de l’eau par

les racines (Huang et Nesmith, 1990). La tolérance à un excès d’eau dans le sol varie entre les

espèces et peut durer de quelques heures à plusieurs jours (Bhattarai et coll., 2005). De plus, les

échanges gazeux peuvent être affectés pendant plusieurs jours après le retour à des conditions

hydriques optimales.

Chaque espèce de plantes a une plage de température pour laquelle sa croissance est optimale.

Généralement, la température à laquelle la photosynthèse est maximale se situe entre 20 et 30 °C

pour les espèces d’angiospermes et gymnospermes boréales, tempérées et tropicales. À des

températures de 40 à 45 °C, la photosynthèse devient nulle chez la majorité des plantes (Teskey et

coll., 2014). Lorsque la température avoisinant les feuilles est supérieure au seuil maximal, le stress

6

thermique qui en résulte peut affecter la croissance et le rendement de la plupart des espèces

végétales. Le stress thermique diminue généralement la durée des phases de développement, la

lumière captée, les processus d’assimilation du carbone et mène à la formation d’organes plus petits

(Stone, 2001).

Lorsque combinés, différents stress peuvent amener des réactions antagonistes. Par exemple,

pendant un stress thermique, les plantes ouvrent leurs stomates pour refroidir leurs feuilles par

transpiration. Cependant, si un stress thermique est combiné avec un stress hydrique, certaines

plantes ne pourront ouvrir leurs stomates et la température de leurs feuilles augmentera (Mittler,

2006). Une gestion efficace de l’eau permet d’éviter les stress hydriques, hypoxiques et thermiques.

1.4. Gestion de l’eau

La gestion de l’eau dans une ferme de canneberges pendant la saison de croissance repose sur

quatre principales techniques permettant d’éviter les stress abiotiques environnementaux. En effet,

l’irrigation par aspersion et l’irrigation souterraine permettent d’éviter le stress hydrique alors que le

drainage permet d’éviter le stress hypoxique. Lors des journées chaudes, l’irrigation par aspersion

peut également être utilisée afin de refroidir le feuillage et éviter le stress thermique.

1.4.1. Irrigation par aspersion

Bien que les premiers systèmes d’irrigation aient été installés par les producteurs pour protéger leur

culture contre le gel dans les années 1960, leur utilisation pour combler les besoins en eau de la

culture pendant les périodes de faibles précipitations s’est par la suite développée (Eck, 1990).

Traditionnellement, l’irrigation était gérée intuitivement par les producteurs ou selon un horaire

fixe. Les travaux de Bonin (2009) ont permis de cibler les seuils de tension de l’eau dans le sol à

respecter afin d’optimiser l’activité physiologique de la plante tout en assurant un flux d’eau

suffisant aux racines. D’importantes économies d’eau et d’énergie sont associées au démarrage de

l’irrigation lorsque la tension de l’eau dans le sol atteint 7.5 kPa dans la rhizosphère, et cela, sans

que le rendement n’en soit affecté (Pelletier et coll., 2013). Lorsque l’irrigation est démarrée à une

tension supérieure à 7.5 kPa, le nombre de fruits par tige, le nombre de fruits total, la grosseur des

fruits et le taux de nouaison sont affectés (Pelletier et coll., 2015). Une conclusion est commune à

tous ces travaux: la zone de confort hydrique pourrait être maintenue par le contrôle de la nappe

phréatique à une profondeur permettant une remontée capillaire suffisante, ce qui entraînerait une

utilisation encore plus restreinte de l’irrigation par aspersion.

7

1.4.2. Irrigation souterraine

L’irrigation souterraine permet d’acheminer l’eau à la rhizosphère par remontée capillaire à partir

de la nappe phréatique afin de réduire les risques de stress hydrique. Lorsque l’eau est prélevée par

les racines ou évaporée à la surface du sol, le maintien d’une nappe constante est possible par

l’ajout d’eau dans l’exutoire du système de drainage. L’eau entre par les drains et remonte dans le

sol jusqu’à l’atteinte de l’équilibre avec le niveau d’eau maintenu dans l’exutoire. Ce niveau d’eau

peut être contrôlé à l’aide d’un barrage dont la hauteur est ajustable selon les besoins de la plante ou

selon la capacité du système de drainage. Lorsqu’un réservoir est situé en amont, l’eau peut être

acheminée à l’exutoire du système de drainage par gravité. Lorsque le réservoir est situé en aval et

que l’eau doit être pompée, l’énergie requise est de 75 à 95% inférieure à celle qu’utiliserait un

système d’irrigation par aspersion (Massey et coll., 1983). En plus de cet avantage, l’irrigation

souterraine permet de diminuer les coûts, de réduire les pertes de nutriments et de pesticides par

lessivage en plus d’augmenter les rendements (Skaggs, 1999).

L’irrigation souterraine a été testée avec succès dans plusieurs cultures, dans plusieurs régions et

sous différents climats. En Argentine, des essais visant à maintenir la nappe à la profondeur

optimale pour différentes cultures ont amené une augmentation de rendement de 270%, de 200%, et

de 80% pour le blé, le maïs et le soya, respectivement (Nosetto et coll., 2009). Dans la période

1996-2008 en Ohio, le rendement du maïs et du soya a été de 29 et 25% supérieur dans les champs

sous irrigation souterraine en comparaison avec des champs en drainage libre (Allred et coll., 2014).

Au Pakistan, 100% des besoins d’irrigation ont été comblés par l’irrigation souterraine pour le blé et

80% pour le tournesol (Kahlown et coll., 2005). Les systèmes de drainage et de circulation de l’eau

installés dans les champs de canneberges du Québec permettraient l’utilisation de l’irrigation

souterraine (Elmi et coll., 2010).

La détermination de la profondeur de nappe à maintenir afin d’assurer une disponibilité en eau et en

oxygène suffisante dans la zone racinaire est donc un prérequis à l’application de l’irrigation

souterraine. Une étude réalisée dans les années 1970 a conclu que la nappe devrait être maintenue à

30-38 cm de la surface du sol afin de maximiser le rendement de la canneberge (Eck, 1976).

Cependant, cette étude a été réalisée antérieurement à l’acquisition des connaissances sur la gestion

de l’irrigation mentionnée ci-haut. Sous conditions contrôlées en cabinet de croissance, Laurent

(2015) a mesuré des taux de photosynthèse et une production de bourgeons supérieurs lorsque la

nappe était maintenue à 60 cm de la surface du sol en comparaison avec des profondeurs de nappe

variant entre 8 et 35 cm. Par simulation numérique, Caron et coll. (2016) ont également conclu

8

qu’une nappe maintenue à 60 cm de profondeur permettrait d’éviter des conditions de stress

hydriques. Cependant, aucune étude n’a été réalisée au champ afin de valider la profondeur de

nappe optimale à maintenir en combinaison avec les nouvelles connaissances sur l’irrigation.

L’irrigation souterraine peut tout de même résulter en une baisse de productivité si l’aération dans

la rhizosphère est insuffisante. Une diminution de la photosynthèse et du rendement ont été mesurés

lorsque la nappe était maintenue trop près du sol (Kalita et Kanwar, 1992; Madramootoo et coll.,

2001; Elmi et coll., 2002).

1.4.3. Drainage

L’utilisation d’un système de drainage efficace permet d’éviter le stress hypoxique dans la

rhizosphère en évacuant les surplus d’eau suite à des précipitations ou des irrigations pour la

protection contre le gel. Bien que non quantifiées, Baumann et coll. (2005) mentionnent que

d’importantes pertes de rendements sont associées à des problèmes de drainage dans les champs de

canneberges. Afin d’évaluer l’efficacité d’un système de drainage, la tolérance de la culture aux

conditions hypoxiques doit être déterminée. Avec des mesures hebdomadaires sur des plantes de

canneberges, Laurent (2015) a mesuré une baisse de photosynthèse dès la première semaine

d’hypoxie et suggère que cette diminution pourrait survenir encore plus tôt. Lors d’une

expérimentation avec de jeunes plants de bleuets, l’assimilation du carbone a diminué de 36% dès le

premier jour de saturation du sol pour atteindre 66% après le cinquième jour (Davies et Flore,

1986). Le même type d’expérimentation avec des cerisiers a mené à une diminution de la

photosynthèse dans les 24 premières heures de saturation du sol et à une diminution de 75% après

cinq jours (Beckman et coll., 1992). Le temps maximal que peut supporter la canneberge en excès

d’eau sans qu’il n’y ait de diminution de productivité est un élément primordial pour évaluer

l’efficacité des systèmes de drainage.

1.4.4. Irrigation de refroidissement

Certains producteurs de canneberges utilisent leur système d’irrigation par aspersion pour refroidir

le feuillage lorsque la température y atteint un seuil cible. Pour une culture de blé, une courte

irrigation de 1.5 mm a permis une réduction de température de la canopée variant de 6.8 à 10.8 °C

(Liu et Kang, 2006). Dans cette étude, le refroidissement était efficace pendant 50-60 minutes et a

permis un gain de rendement de 4.3%. Dans une production de pommes, cette technique s’est

avérée efficace pour réduire la quantité de blessures aux fruits associées aux températures élevées

(Parchomchuk et Meheriuk, 1996) ainsi que pour augmenter le rendement (Iglesias et coll., 2005).

Dans une production de poires, la température a été réduite entre 3.8 à 5.5 °C suite aux événements

9

d’irrigation de refroidissement lorsque la température de l’air atteignait 29 °C (Dussi et coll., 1997).

La couleur des fruits était de qualité supérieure et la maturation des fruits était plus rapide dans les

parcelles refroidies. Pour que l’utilisation de l’irrigation de refroidissement soit efficace, la

température où le stress thermique survient doit être identifiée. Cependant, cet élément est inconnu

pour la canneberge.

1.5. Problématique

La plus récente littérature expose le potentiel du contrôle de nappe en production de canneberges

afin de répondre à la nouvelle contrainte de l’industrie : augmenter le rendement et sa qualité tout

en diminuant l’impact sur l’environnement. Cependant, l’étude du rendement en fonction de la

profondeur de nappe remonte à plusieurs décennies et doit être actualisée en fonction des nouvelles

connaissances sur le seuil de démarrage de l’irrigation par aspersion et sur la zone de confort

hydrique de la canneberge. En utilisant l’irrigation par aspersion lorsque la tension de l’eau dans le

sol atteint le seuil critique en supplément au contrôle de nappe permettrait en tout temps de combler

les besoins en eau de la plante et de maximiser son rendement agronomique.

Le maintien d’une profondeur de nappe constante augmente le risque d’engendrer des conditions

hypoxiques dans la rhizosphère suite à une précipitation ou une irrigation de protection contre le

gel. En plus de maintenir la nappe à une profondeur permettant de combler les besoins en eau de la

plante par remontée capillaire, le système de drainage devra permettre d’évacuer les surplus d’eau

en respectant la durée que la canneberge peut tolérer des conditions hypoxiques sans subir de baisse

de productivité. Cependant, la tolérance de la canneberge aux conditions hypoxiques est à ce jour

inconnue.

Le contrôle de nappe menant à une réduction de la fréquence d’irrigation, le microclimat entourant

les vignes s’en retrouve modifié en comparaison avec de fréquentes irrigations. En effet, une

irrigation traditionnelle de quelques heures en matinée a pour effet de maintenir l’humidité plus

élevée et la température plus basse dans le feuillage en comparaison avec le contrôle de nappe. Le

déficit de pression de vapeur dans l’air entourant le feuillage sera plus élevé avec le contrôle de

nappe, augmentant ainsi les risques de stress thermique lorsque le prélèvement racinaire est

inédaquat. Une courte irrigation de mi-journée lorsque la température de l’air dans le feuillage

atteint un seuil critique peut être bénéfique pour la plante en favorisant la photosynthèse par la

réduction du déficit de pression de vapeur dans l’air entourant le feuillage. Cependant, bien que le

10

seuil de température où survient le stress thermique soit connu dans le cas de plusieurs cultures, il

demeure pour l’instant inconnu pour la canneberge.

La détermination de la profondeur de nappe adéquate, de la durée de tolérance de la plante à des

conditions hypoxiques, des pertes de rendements associées aux problèmes de drainage et de la

température critique compose une problématique qui doit être résolue pour le développement d’une

approche intégrée de la gestion de l’eau en production de canneberges. Bien que les impacts de la

profondeur de nappe et des problèmes de drainage puissent être déterminés in situ par l’évaluation

du rendement de la culture à la fin de la saison, les stress thermiques et hypoxiques doivent être

étudiés lors d’événements spécifiques. Dans ces conditions, la caractérisation des échanges gazeux

est la mesure la plus adaptée, car la revue de littérature a démontré qu’une diminution de la

photosynthèse est l’une des premières réponses observées suite à ces stress. Puisque le carbone

assimilé par la photosynthèse sera éventuellement stocké dans les fruits, le taux de photosynthèse

est généralement corrélé au rendement agronomique de la culture. Afin de valider l’hypothèse

permettant de répondre à la problématique soulevée, certains objectifs ont été formulés et sont

présentés à la section suivante.

1.6. Objectifs

L’objectif principal de cette thèse est de développer une approche intégrée de la gestion de l’eau en

production de canneberges afin de limiter l’impact des principaux stress environnementaux. Afin de

résoudre la problématique soulevée à la section précédente et de répondre à cet objectif principal,

les quatre objectifs secondaires suivants ont été formulés:

Déterminer la profondeur de nappe optimale permettant une remontée capillaire suffisante

pour combler les besoins en eau de la plante, maximiser le rendement et favoriser un

drainage adéquat. (Expérience au champ)

Déterminer l’effet de la durée de saturation du sol (conditions hypoxiques) sur la

photosynthèse et sur son taux de récupération. (Expérience en chambre de croissance)

Vérifier l’impact potentiel du stress hypoxique en quantifiant les pertes de rendements

associées à des problèmes de drainage. (Études de cas)

11

Déterminer la température maximale que peut tolérer la plante sans baisse de photosynthèse

et évaluer l’efficacité de l’irrigation de refroidissement pour éviter le stress thermique.

(Expérience au champ et en chambre de croissance)

Chacun de ces objectifs a été développé dans les chapitres suivants.

12

CHAPITRE 2 Water Table Control for Increasing Yields and Water Savings in Cranberry Production

Vincent Pelletier1, Jacques Gallichand1, Silvio Gumiere1, Steeve Pepin1 and Jean Caron1

1Département des sols et de génie agroalimentaire, Université Laval, 2425 rue de l’Agriculture, Université Laval, Québec, Québec, Canada, G1V 0A6;

13

Résumé. L’utilisation du contrôle de nappe en production de canneberges a permis d’améliorer la

durabilité des pratiques culturales reliées à la gestion de l’eau. Dans la province de Québec

(Canada), trois sites ont été investigués afin de déterminer la profondeur de nappe (PN) optimale

répondant aux trois critères suivant: (1) augmenter les rendements sans toutefois diminuer la qualité

des fruits; (2) minimiser l’utilisation du système d’irrigation par aspersion et; (3) éviter les

conditions hypoxiques dans la rhizosphère. Les résultats ont démontré que le rendement final, la

concentration en sucre des fruits, le nombre de fruits total, le nombre de fruits par tige, et le taux de

nouaison étaient maximisés lorsque PN était à 60 cm. L’utilisation de l’irrigation par aspersion a été

réduite de 77% lorsque PN était inférieure à 66 cm. Dans le but d’éviter les conditions hypoxiques

associées à un drainage lent, le niveau d’eau dans les canaux entourant les champs devrait être

abaissé à 80 cm sous la surface du sol lorsqu’une précipitation ou une nuit de protection contre le

gel est anticipée. Les champs situés sur un même niveau devraient être entourés par des canaux afin

d’assurer une PN uniforme tout en évitant les pertes d’eau par écoulement périphérique causées par

des gradients hydrauliques latéraux.

14

Abstract. Water table control has been successfully tested to improve the sustainability of water

management in cranberry production. In the province of Québec (Canada), three sites were

investigated to determine the optimum water table depth below soil surface (WTD) using three

criteria: (1) increasing yield without decreasing fruit quality; (2) minimizing the amount of water

needed by the sprinkler system; and (3) avoiding hypoxic stresses in the rhizosphere. Our results

show that the final yield, the berry sugar content, the total number of berries, the number of berries

per upright, and the fruit set were maximized when the WTD was 60 cm. Sprinkler water savings of

77% were obtained where the WTD was shallower than 66 cm. In order to avoid hypoxic conditions

due to poor drainage, the water level in the canals surrounding the beds should be lowered to 80 cm

when a rainfall or a frost protection irrigation is anticipated. All sides of a block of beds must be

surrounded by canals to ensure a uniform WTD and to avoid lateral hydraulic gradients that could

cause peripheral seepage losses.

15

2.1. Introduction

More than 98% of cranberries (Vaccinium macrocarpon Aiton) are produced in North America

(FAOSTAT, 2015). The beginnings of cranberry cultivation go back to the early years of the 19th

century in the state of Massachusetts, USA (Eck, 1990). Massachusetts was the world leader in

cranberry production until the 1990s, when the state of Wisconsin, USA, became the largest

cranberry producing area. In 2014, the province of Québec, Canada, was the second most important

cranberry producer with 110 000 tons for a cultivated area of 3450 ha. The Québec average yield

(2005–2014) has increased by 66% from the previous decade (1995–2004) (APCQ, 2015). Part of

this increase could be due to a better understanding of hydrological processes and application of

related recommendations to water management in cranberry beds. Health benefits related to

antioxidant components, such as anthocyanin, have led to an increase in the demand for cranberry

over the last few years. Despite its high sugar content, the high concentration in titratable acidity

causes the bitter taste of cranberry. The most important yield components related to final yield are

the number of marketable berries per area, the number of fruiting uprights per area, the number of

marketable berries per upright, and the fruit set (Pelletier et al., 2015). Flower buds are formed

during the summer of the previous year while berries formed in early July grow until harvest in

October.

Recent developments in wireless communication technology have allowed online soil moisture and

air temperature monitoring and real-time irrigation management. For maximizing yield, yield

components, and water productivity, there is evidence that the pump should be turned on when soil

water tension (SWT) at 10 cm depth in the root zone reaches 7.5 kPa (Pelletier et al., 2013; Pelletier

et al., 2015; Caron et al., 2016). Cranberry evapotranspiration ranges between 0.5-4.0 mm day−1 in

Washington (Hattendorf and Davenport, 1996) whereas the maximum value was found to be 5.0

mm day−1 in Wisconsin (Bland et al., 1996).

Recent work demonstrates that cranberry is a species sensitive to hypoxic conditions in the

rhizosphere. When the SWT is lower than 3.0 kPa, gas exchange and plant productivity are reduced

(Caron et al., 2016; Laurent, 2014). For evacuating the excess of water in the soil profile after

rainfall, subsurface drainage systems are used. Plastic pipes, 10 cm in diameter, are buried with

outlets in canals surrounding the beds. This drainage system allows the WTD to be controlled by

adjusting the water level between the reservoir and the drain tubes. Actual drainage systems in

cranberry farms have the potential to be used as water table control system, meeting the crop water

requirements during the season (Elmi et al., 2010). It is in fact a combination of drainage and

16

subirrigation. Controlling the WTD could considerably reduce the energy and water needed by

sprinkler irrigation in cranberry production (Gumiere et al., 2014). When upward water fluxes from

the water table are sufficient to support plant transpiration and soil evaporation, the use of sprinkler

irrigation is reduced. However, attention should be given in order to avoid waterlogging caused by a

too shallow water table and to ensuring fast drainage, even more so with global warming and the

potential for increased rainfall intensities (Mailhot et al., 2010). Another risk of maintaining shallow

water tables is to increase soil salinity; however, experiments have shown that even applying three

times the recommended potassium fertilizer amount does not cause plant stress due to salinity

(Samson et al., 2013).

Water table control has been tested for different crops and regions around the world and identified

as the best water management practice for reducing the environmental impact and maintaining or

enhancing crop yield (Madramootoo et al., 2001; Evans et al., 2015). Determining the optimal

WTD for cranberries is then of first importance for using water table control. For early rooting and

vegetative growth, growth rate was greatest and rooting depth shallowest with rooted cuttings

grown in a greenhouse under WTD at 13 cm compared to 39 and 57 cm (Baumann et al., 2005), and

similar results were obtained with WTD at 6 cm in comparison with 35 cm (Hall, 1971). For

established beds, based on the soil moisture-WTD relationships, crop water requirements could be

supplied through capillary rise with a WTD at 30-50 cm (Handyside, 2003), or 40-60 cm (Caron et

al., 2016), and a very high risk of water stress for the crop could result from a WTD at 80 cm

(Caron et al., 2016). Maintaining a WTD at an average of 60 cm led the photosynthesis rate and the

number of buds produced to be maximized compared to treatments with WTD ranging from 8-35

cm, explained by a lack of oxygen in the root zone in the shallowest WTD treatments (Laurent,

2014). With no sprinkler irrigation in addition to capillary rise, higher fruit yields resulted from a

30-38 cm WTD in three out of five years when compared to 38-46 cm and in four out of five years

when compared to 46-54 cm (Eck, 1976). Consequently, it appears that maintaining an optimal

WTD combined with sprinklers would maximize established bed cranberry yields, minimize the use

of sprinkler irrigation, and meet the drainage requirements.

The objective of this work was to determine the optimal WTD using three criteria: (1) maximizing

yield without affecting the fruit quality; (2) minimizing the use of sprinkler irrigation by avoiding

SWT above 7.5 kPa; and (3) ensuring fast drawdown of the water table to 40 cm deep (SWT = 3.0

kPa in the root zone) after rainfall and frost irrigation events. Soil water characteristics were

initially used to approximate the optimal WTD which was then verified during a two-year field

experiment.

17

2.2. Experimental section

Experiments were conducted in 2013-2014 on both conventional and organic cranberry production

farms in Québec. One section of beds was used at the conventional farm as Site A and two

separated sections of beds were used as Site B and C at the organic farm. Detailed characteristics of

each site are given in Figure 2.1 and in Table 2.1. All beds were isolated from one another by a 5-m

wide dike. The four sides of Site A were surrounded by canals. Bed 4 was not used because it was

not the same cultivar. For site B, only three sides were surrounded by canals, and the fourth side

consisted in a cranberry bed one meter lower than the experimental beds. One side of Site C

consisted in a cranberry bed on the same level than the experimental beds whereas the three other

sides are surrounded by canals, but the one canal on the southeast side is only 60-m long. The

experimental beds were all on the same level at each site.

Figure 2.1. The experimental sites.

Table 2.1. Characteristics of the experimental sites.

Characteristic Site A Site B Site C

General information

Location 46°16’ N – 71°57’W 46°17’N – 71°59’W 46°16’ N – 72°01’W

Production Conventional Organic Organic

Bed properties

Number of beds 6 3 3

Dimensions of one bed (m x m) 457 x 46 479 x 52 404 x 52

Subsurface Drainage

Spacing (m) 11.4 15.2 15.2

Depth (m) 0.8 0.8 0.8

Slope (%) 0.07 0.13 0.15

Sprinklers system

Sprinkler spacing (m) 18 15 15

Irrigation line spacing (m) 15 18 18

18

Monthly climatic data, from a public weather station located 8 km away from Site A and 5 km away

from sites B and C, are given in Table 2.2. Air temperature and growing degree days (GDD) for

both years of the experiment were similar to long term averages. The April to September average

air temperature was 14.2 °C in 2013, 14.4 °C in 2014, and 13.9 °C for the 1981-2010 period while

GDD was 1757 in 2013, 1768 in 2014 and the average was 1715 for the 1981-2010 period. The

total rainfall during the growing season of 2013 (666 mm) was similar to that of the long term (660

mm), but was 15% less in 2014 (563 mm). July was drier than the average for both years with

approximately 34% less rainfall than the normal for that month.

Soil texture at the three sites is representative of the cranberry soils with 100% of sand. Weight

fractions were 5%: very fine sand, 54%: fine sand, 36%: medium sand and 5%: coarse sand. The

soil water retention and the hydraulic conductivity curves of the soil in the rhizosphere are shown in

Figure 2.2. Saturated hydraulic conductivity is about 150 mm h-1 and saturated and residual

volumetric water content are 0.34 and 0.05, respectively (mean values of all three sites). When

SWT is below 2.0 kPa (WTD < 30 cm), soil is mostly saturated and this situation could result in

hypoxic conditions in the rhizosphere. The hysteresis effect is an important consideration in these

soils. When SWT is above 8 kPa (WTD > 90 cm), upward fluxes are negligible which would

increase the need for sprinkler irrigation. Hence, from these soil water characteristics, it appears that

the optimal WTD should be in the range of 30-90 cm for both sufficient upward flux and adequate

drainage, and consequently WTD treatments were chosen to cover that range.

Table 2.2. Monthly climatic data at the experimental site in St-Louis-de-Blandford, Québec, Canada and long term averages from a public weather station located 8 km away from Site A and 5 km away from sites B and C.

April May June July August September

Air Temperature (°C)

2013 4.5 13.5 15.4 20.5 18.0 13.4

2014 3.9 12.3 18.2 19.8 18.4 13.7

Ave 1981-2010 4.3 11.4 16.7 19.3 18.1 13.6

GDDz

2013 52 255 312 472 408 258

2014 30 229 376 460 409 264

Ave 1981-2010 48 203 353 443 407 261

Rainfall (mm)

2013 38 153 126 87 144 118

2014 123 59 106 86 133 56

Ave 1981-2010 66 106 127 130 119 112

z: Growing Degree Days (5 °C based)

19

Figure 2.2. (a) Volumetric soil water content and (b) hydraulic conductivity in relation with soil water tension. The curves represent the average of all three sites.

At Site A, the weir at the outlet of the surrounding canals was adjusted 70 cm deeper than the beds’

soil surface during the growing season. Since this block of beds is located at the bottom part of the

farm, drainage water continuously flowed from the upstream beds, ensuring the water level to be

constant with the weir setting. In order to maintain shallower WTDs, 5 cm inside diameter plastic

pipes were installed between the reservoir and the drainage inlet to maintain the WTD at 50 cm in

Bed 2, 3, and 6. A float valve was installed on each drain tube inlet to stop water flowing when the

equilibrium was reached. Therefore, at Site A, the targeted WTD was 70 cm in beds 1, 5, and 7, and

50 cm for beds 2, 3, and 6. The only form of energy used for adding water to drain tubes was

gravity. At Site B, the weir at the outlet of the surrounding canals was adjusted to a depth of 60 cm

from the soil surface of the beds. Since these beds are located at the upper position in the farm,

water was pumped into the canals when the water level in the canals was 70 cm deeper than the

beds soil surface. At Site C, the weir at the outlet of the surrounding canals was adjusted to a depth

of 50 cm from the soil surface of the beds and only gravity was used to move water from the

reservoirs to the drain tubes.

For investigating the uniformity of the WTD, a total of 133 observation wells have been installed in

2013 and 242 in 2014. Readings were taken once a week with a dipper-T water level indicator from

Heron Instruments Inc. (Dundas, Ontario, Canada) and recorded manually. The wells were made

from PVC pipes (10 cm outside diameter) cut in 150 cm sections. Holes and diagonal saw cuts were

made in each pipe to let the water enter. The bottom of the pipe was sealed with a PVC cap and

adhesive. Boreholes were mechanically augured and wells closely fitted inside each borehole. The

upper pipe opening was protected with a PVC cap with no adhesive. Wells were distributed to

uniformly cover the beds. The WTD data were mapped with the Thin Plates Splines (TPS) method

20

which had been found to be the best spatial interpolator for soil and yield parameters in cranberry

fields (Gumiere et al., 2014).

At the three sites, sprinkler irrigation was used to complement water table control when the upward

fluxes from the water table were not sufficient to meet evapotranspiration. At Site A, Beds 2, 3, and

6 were managed separately from Beds 1, 5, and 7. Only one irrigation zone was set in 2013 at Site

B, but due to drier conditions in Bed 3, it was managed separately from Beds 1 and 2 in 2014. Each

bed was equipped with two wireless HXM-80 tensiometers from Hortau (Lévis, QC, Canada),

installed at a depth of 10 cm below the soil surface. Readings were taken at 15 min intervals and

sent, via a wireless communication system, to the Irrolis website (www.hortau.com, Lévis, Canada)

for processing. Irrigation was initiated when the average SWT value in a given irrigation zone

reached the threshold value of 7.5 kPa, unless at that time the rainfall probability exceeded 80%. In

that case, irrigation was postponed until the rainfall probability dropped below 80%. Standard

farming practices (fertilization, pesticide application, pollination, etc.) have been done according to

the growers calendars.

Crop yield was evaluated by manually harvesting berries from four 1075 cm2 rings around each

observation well. The distance between any two rings was at least 3 m. Yield values were also

interpolated and mapped with the TPS method (Gumiere et al., 2014). Mean berry weight was

calculated as the weight of 100 marketable berries taken randomly within each ring. The number of

berries per ring was calculated as the total weight of the berries divided by the mean berry weight.

Berries were counted and weighed on-site. In three 182 cm2 rings per bed, the number of fruiting

uprights, the number of marketable and non-marketable berries, and aborted flowers per upright

were counted. Fruit set was then computed as the number of berries divided by the sum of berries

and aborted flowers. Parameters of fruit quality were evaluated on two samples per bed. In order to

use the same berries, each berry was cut in three equal parts for testing total soluble solids (TSS),

total anthocyanin (TAcy), and titratable acidity (TA). Berries were crushed to obtain a juice sample

for measuring TSS (as Brix) with a HI-96811 temperature-compensating refractometer from Hanna

Instruments (Woonsocket, Rhode Island, USA). The TAcy (mg/100 g FW of berries) was

determined by the accelerated solvent extraction method (Fuleki and Francis, 1968) using a

Genesys 6 spectrophotometer from Thermo Fisher Scientific Inc (Rochester, NY, USA) while TA

was measured from titration of NaOH 0.1 N to a pH 8.20 end point and expressed as g/L of tartaric

acid. As an evaluation of the taste perception, the ratio of TSS on TA was computed. In addition to

linear regressions, the boundary line approach was used to establish the optimum WTD as this

21

method has been suggested for data where the field environmental conditions cannot be controlled,

but may have a strong influence on variability (Webb, 1972).

2.3. Results and discussion

2.3.1. First criteria: Increasing yield without decreasing fruit quality

Relationship between yield and WTD

The maximum yield and the highest number of berries were observed when WTD was

approximately 60 cm (Figure 2.3). Hypoxic stress could be more damaging than water stress since

for each WTD step of 10 cm, the yield increased by 15% between 25 and 60 cm and decreased by

8% between 60 and 120 cm. Those results are consistent with recent studies under controlled

conditions where plant activity was maximized when WTD was approximately 60 cm, but reduced

in the range of 30-50 cm due to soil aeration limitation (Caron et al., 2016; Laurent, 2014).

However, our findings differ from older studies where the authors concluded that WTD should be

maintained between 30-50 cm based on soil water characteristics only (Handyside, 2003) or

between 30–38 cm when yield were considered, but without the use of sprinkler irrigation (Eck,

1976). Improving water management by using sprinkler irrigation, with a threshold of 7.5 kPa, in

addition to WTD control could explain the deeper optimal water table found in our study compared

to previous studies. Moreover, deeper WTD promotes faster drainage and will be discussed in

Section 3.3.

Figure 2.3. Boundary line approach of (a) yield and (b) number of berries in relation with the averaged water table depth (WTD) during the growing season of 2014 at Site A ( ), Site B ( ), and Site C ( ). Each value represents the average yield of four 1075 cm2 rings harvested around each observation well relatively to the maximum yield at each site.

0%

20%

40%

60%

80%

100%

0 20 40 60 80 100 120

Relative

 Yield

WTD (cm)

a

0%

20%

40%

60%

80%

100%

0 20 40 60 80 100 120

Relative

 number of berries

WTD (cm)

b

22

Mapping the WTD

The averaged observed WTD at Site A was 60 ± 12 cm in 2013 (Figure 2.4a) and 64 ± 13 cm in

2014 (Figure 2.4b). The root square mean error (RSME) of the map was 4 cm for the 2013 values

and 2 cm for the 2014 values. The WTD was close to 50 cm where water was added at the northeast

end of Bed 2 and Bed 3. Although there is a 2 m deep canal at the southwest end of the block and

that the water level in that canal was 70 cm below the soil surface, the WTD dropped from 70 to

100 cm deep within 70 m of the canal. There is another block of beds located 1 m lower

downstream (on the right side in Figure 2.4a) and this suggests that the soil below the ditch is not

impermeable, which would result in a hydraulic gradient and seepage losses between the two blocks

of beds. The average WTD measured in the observation wells at Site B are shown in Figure 2.4c for

2013 and in Figure 2.4d for 2014. The RSME is less than 1 cm for both maps. For both years, the

WTD in Bed 1 and Bed 2 were in the desired range of the 50–70 cm, but the WTD in Bed 3 was

deeper. There was a gradient in the WTD transverse to the width of the bed caused by Bed 4 (not

shown) which soil surface was 1 m lower than that of Bed 3. Water added in the drain tubes of Bed

3 was probably lost to Bed 4 by lateral seepage. The average WTD for Site C was 69 ± 21 cm in

2013 (Figure 2.4e) and 60 ± 8 cm in 2014 (Figure 2.4f). The RSME of the maps is less than 1 cm

for both the 2013 and 2014 values. For both years, the WTD was deeper in the southwest part of the

beds due to an adjacent block of beds 1 meter lower downstream, as found in Site A. In 2013

(Figure 2.4e), the white zone means that the WTD was deeper than the depth of the observation

wells (120 cm).

a. Site A - 2013

23

b. Site A - 2014

c. Site B - 2013

d. Site B - 2014

e. Site C - 2013

f. Site C - 2014

Figure 2.4. Filled contour of weekly average water table depth for the three sites between June and September in 2013 and 2014. Crosses represent observation wells.

24

Mapping the yield

The average yield at Site A was 59164 kg ha−1 and the RMSE of the model is 10614 kg ha−1 (Figure

2.5a). Only two spots in the beds yielded less than 50000 kg ha−1 and this is because they were

planted with a different cultivar yielding smaller berries (Figure 2.5a). Indeed, the number of berries

in those spots was similar to the number of berries in the rest of the beds. Prior to the water table

control experiment, the five-year average yield at this site was 39254 ± 6700 kg ha−1 with sprinkler

irrigation used as the only water management system, i.e., with the water table uncontrolled. The

average yield at Site B was 39273 kg ha−1 with a RSME of 5229 kg ha−1 (Figure 2.5b). Site C yielded

an average of 29989 kg ha−1 (Figure 2.5c) with a RSME of 6876 kg ha−1. The yield was uniform

except in the south corner of Bed 1 where it was approximately 10000-15000 kg ha−1 lower. In this

region, an unusual two-day episode of heat stress (air temperature >28 °C) when plants were

breaking dormancy in May 2013 coupled to a very deep water table (>150 cm) resulted in plants

reaching the permanent wilting point. In 2013, there was no fruit produced in this area of the bed.

Before this high mortality event, the water level in the canal in the south part of the corner was not

controlled and mostly empty. The bottom of the canal was approximately 2 m deeper than the soil

surface in Bed 1. Some excavation work was carried out in the spring of 2014 to connect that canal

to the canal at the northwest end of the block of beds to maintain water level at the required depth in

the canal. Following that modification, WTD in that corner was 70 cm shallower than in 2013, and

the yield returned to normal.

Such trials suggest that top yields could be achieved for this production with this irrigation method.

Indeed, the average yield at Site A was 79% higher than the 2014 Québec average conventional

production yield (APCQ, 2015). Recent studies in Québec have already reported yield samples as

high as 66000 kg ha−1 (Marchand et al., 2013) although it was established 25 years ago that the

potential for cranberry production would be approximately 57000 kg ha−1 with all factors being

optimum (Eck, 1990). At Site A, 57% of the samples harvested exceeded that potential threshold,

28% were greater than 70000 kg ha−1, 6% of the samples were greater than 80000 kg ha−1 and the

highest yield was 95231 kg ha−1, pushing the cranberry potential much higher than previously

established. The yield at Site B was 62% greater than the 2014 Québec organic cranberry

production average yield. The maximum yield in one sample was 63456 kg ha−1 and even with

organic production, 3% of the samples yielded more than the 57000 kg ha−1 established cranberry

potential. Before the water control experiment, the four-year average yield for this site was 22785 ±

8202 kg ha−1 with sprinkler irrigation as the main water management system, i.e., with the water

25

table uncontrolled. Based on these results, it can be clearly stated that water table control can be a

powerful tool to increase the yield in cranberry production.

Three possible causes can be identified to explain the exceptionally high yields at the experimental

sites. The first reason is that water supply in the root zone is steadier with subirrigation compared to

sprinkler irrigation. The second reason is that fertilizers are generally available to the roots for a

longer period of time with subirrigation by reducing leaching. With frequent sprinkling, fertilizers

are leached with soil solution below the root zone. The third reason is that leaves are kept drier

when water table control is used instead of sprinkler irrigation, allowing better conditions for the

plants to fix carbon by photosynthesis. Resource limitation has long been pointed out as a potential

yield limitation factor in cranberries. Greater energy reserves stocked as carbohydrates could allow

more berries to be set from flowers and then increase final yield (Brown and McNeil, 2006;

Birrenkott et al., 1991; Hagidimitriou and Roper, 1994).

Yield components

The yield component most significantly affected by the WTD was fruit set (Figure 2.6a), where the

maximum was found at a WTD of 60 cm. At that value, the maximum fruit set on the regression

curve was 52%, but when WTD was 15 cm deeper, fruit set was reduced to 35% (Figure 2.6a),

leading to a decline in the total number of berries (Figure 2.3b). When the water table was deeper

than 60 cm, significantly fewer berries per upright were also found (Figure 2.6b). On the regression

curve, a maximum of 1.90 berries/upright corresponded to a WTD of 60 cm, but this value was

reduced to 1.28 when WTD was only 15 cm deeper. This lower number of berries was not

compensated by other components since berry weight (Figure 2.6c) and the number of fruiting

uprights per sample (Figure 2.6d) were not significantly affected by WTD (p >0.05). The average

number of fruiting uprights was 53 ± 18 per sample ring and the average of berry weight was 1.73 ±

0.18 g. Multiplying these two averages by the number of berries per upright gives a predicted yield

increase of 30563 kg ha−1 when the WTD is raised from 75 to 60 cm; and this even when sprinkler

irrigation is used as a complementary source of water. Maintaining the WTD at the optimum value

is thus important for increasing final yield.

The high values of the yield components can explain the high yield found in our experiment. Water

limitation was also previously associated with a significant reduction of the number of berries per

upright and fruit set leading to a significant reduction of final yield (Pelletier et al., 2015). When

root water uptake is less than the potential evapotranspiration, which is caused by insufficient water

fluxes, cranberries transpiration is affected and photosynthesis is reduced (Caron et al., 2016).

26

Upward fluxes are negligible when the WTD is deeper than 90 cm (Figure 2b). Cranberry yield

limitation is often explained by the low success of flowers to produce berries caused by a limited

accumulation of carbohydrates (Brown and McNeil, 2006; Birrenkott et al., 1991; Hagidimitriou

and Roper, 1994). Since water availability has been identified to limit carbon fixation (Caron et al.,

2016), controlling the water table at a depth deeper than the optimum probably resulted in lower

plant energy reserves available to set fruits. The optimum seasonal averaged WTD has been found

to be 60 cm and attention should be paid to avoid water tables deeper than 75 cm.

a. Site A

b. Site B

c. Site C

Figure 2.5. Crop yield at the three sites in 2014. Crosses represent samples location.

Insufficient water fluxes from water tables that were too deep also negatively affected the yield

components in other crops in Québec. Subirrigation treatment produced significantly more maize

cobs and grain yields were twice as high as the nonirrigated treatment (Nemon et al., 1987). Also in

maize, when the water table was deeper than the optimum, the number of ears per square meter, the

number of grains per square meter, the number of grains per row and the grain weight were reduced

27

(Nosetto et al., 2009). Pods and seed number per plant were lower for the 100 cm WTD than for the

40–80 cm WTD in soybean grown on a sandy loam (Madramootoo et al., 1993).

Figure 2.6. Yield components in relation with the averaged water table depth (WTD) during the growing season at Site A ( ), Site B ( ), and Site C ( ). (a) Percentage of fruit set per flower; (b) Number of berries per fruiting upright; (c) Berry weight (d) Number of fruiting uprights per ring of 182 cm2. (Solid line: Regression line; Dashed line: Boundary line approach). The R2 and p values are for the regression lines.

Fruit quality parameters

The quality parameters of the berries in relation with WTD are shown in Figure 2.7. The

relationship between TSS and WTD was significant (p < 0.05) and the maximum was found when

the average WTD during the growing season was between 60-70 cm (Figure 2.7a). Although the

relationships between the ratio of TSS to TA (Figure 2.7b), TA (Figure 2.7c), and TAcy (Figure

2.7d) with WTD were not significant (p > 0.05), the maximum of those parameters were found

between 60-70 cm with the boundary line approach. Water stresses also affected yield quality in

other crops, but the effect was contradictory depending on the geographical area, crops and studies.

In Florida, sugar yield from sugarcane plants was significantly lower when the WTD was 75 cm in

comparison with 45 cm (Pitts et al., 1993). Deficit irrigation increased TSS and TAcy in grapevines

in Chile (Acevedo-Opazo et al., 2010) and in U.S.A. (Song et al., 2012), as is generally known to

do, but another study concluded to the contrary in Italy (Lanari et al., 2014). Based on the first

25%

35%

45%

55%

65%

75%

45 50 55 60 65 70 75 80

Fruit Set

WTD (cm)

R2 = 0.31p < 0.01a

0,0

0,5

1,0

1,5

2,0

2,5

45 50 55 60 65 70 75 80

Berries / Upright

WTD (cm)

R2 = 0.30p = 0.05b

1,2

1,4

1,6

1,8

2,0

2,2

45 50 55 60 65 70 75 80

Berry weight (g)

WTD (cm)

R2 = 0.05p = 0.93c

0

20

40

60

80

100

45 50 55 60 65 70 75 80

Fruiting Uprights / Sam

ple

WTD (cm)

R2 = 0.05p = 0.97d

28

criteria, the average WTD should be 60 cm for increasing crop yield without negatively affecting

yield quality.

Figure 2.7. Yield quality parameters in relation with the averaged water table depth (WTD) during the growing season at Site A ( ), Site B ( ), and Site C ( ). (a): Total soluble solids (TSS); (b) Titratable Acidity (TA); (c) Ratio of TSS on TA; (d) Total Anthocyanin (TAcy). (Solid line: Regression line; Dashed line: Boundary line approach). The R2 and p values are for the regression lines.

2.3.2. Second criteria: Minimal use of sprinkler irrigation

Irrigation was started when the average SWT in individual irrigation zone reached 7.5 kPa. Since

the tensiometers were installed in the rhizosphere at 10 cm depth, a SWT of 7.5 kPa means a WTD

of 85 cm at the equilibrium and in a uniform soil profile. Seasonal sprinkler irrigation requirements

were between 0 and 48 mm when the WTD was between 52 and 65 cm whereas they were between

72 and 168 mm when the WTD was between 66 and 90 cm (Table 2.3). Maintaining the WTD

shallower than 65 cm saved considerable amount of sprinkler irrigation water in comparison with a

deeper WTD. Similar results were obtained by numerical modeling studies (Gumiere et al., 2014).

Without considering upward flux from the water table, it has been established that cranberry needs

approximately 300 mm of water from sprinkler irrigation (Binet et al., 1997; Sandler et al., 2004).

Controlling the WTD has then been successful for reducing water needs. The contribution of

groundwater in meeting the crop water requirements was 100% in wheat and 80% in sunflowers

and the relation was also a function of the WTD (Kahlown et al., 2005).

7

8

9

10

11

12

30 40 50 60 70 80 90 100

Brix (%

)

WTD (cm)

R2 = 0.23p = 0.02a

2,0

2,5

3,0

3,5

4,0

30 40 50 60 70 80 90 100

Brix / TA

WTD (cm)

R2 = 0.09p = 0.13

b

2,5

3,0

3,5

4,0

30 40 50 60 70 80 90 100

TA (%acid)

WTD (cm)

R2 = 0.03p = 0.37

c

15

25

35

45

55

30 40 50 60 70 80 90 100

TAcy (mg / 100g) 

WTD (cm)

R2 = 0.05p = 0.81

d

29

When the soil is drier than 7.5 kPa and sprinkler irrigation has not yet been turned on, the SWT is

rapidly increasing during daytime and starts to fall when the evapotranspiration demand decreases

during nighttime. Such changes in SWT were observed in Bed 3 at Site B and in Bed 1 West at Site

3 when the WTD and SWT were outside the hydric comfort zone (Figure 2.8). More frequent

sprinkler irrigations could have avoided this situation. When the water table is deeper than 90 cm,

the upward flux is negligible and the roots need to provide more energy for an active water uptake

as the change in soil water content is low for each additional kPa of SWT (Figure 2.2a).

Table 2.3. Irrigation water applied at each site for 2013-2014 and weekly averaged water table depth (WTD).

Site Beds 2013 2014

Irrigation (mm) WTD (cm) Irrigation (mm) WTD (cm)

A 1-5-7 36 52±15 48 65±16

2-3-6 24 58±18 36 60±16

B 1-2 120 72±9 72 66±12

3 120 89±12 168 75±12

C 1 West 102 90±12 144 75±8

1 East-2-3 0 61±9 24 58±9

Mostly no rain was recorded from day of year (DOY) 179 to 198 in 2013 and from DOY 177 to

DOY 207 in 2014. This represented the flowering and fruit set periods, the most sensitive

cranberries development stages to water stress (Pelletier et al., 2015). With no rain for several

consecutive days, the water table control system was unable to keep the water table at the desired

depth; this led to a lowering of the water table where the upward flux was insufficient to meet the

evapotranspiration demand. Sprinklers were turned on only during these dry periods at Site A for

both years. At Site C, except for Bed 1 West, no irrigation was needed in 2013 and two irrigations

were needed in 2014. Since no modification was done to the laterals drain depth or spacing,

optimization of those parameters in the design of future beds could be effective to completely avoid

the sprinkler irrigation even during the driest periods of the growing season.

At Site B in 2013, sprinkler irrigation was applied when the average of the six tensiometers reached

7.5 kPa. However, SWT in Bed 3 was always higher than in Beds 1 and 2 (Figure 2.8) due to a

deeper water table, by 12 cm on average, than in Beds 1 and 2 (Figure 2.4c); this was likely caused

by the problem of water leaks from the drains of Bed 3 to Bed 4, as previously explained. Sprinklers

were turned on when SWT was lower than 7.5 kPa in Beds 1 and 2, resulting in water being

unnecessarily applied in those beds, but higher than 7.5 kPa in Bed 3, leading to water stress. To

avoid that situation, two irrigation zones were created in 2014 and Beds 1 and 2 received 57% less

water than Bed 3. Our results are similar to numerical simulations that concluded that irrigation can

30

be reduced by 75% when beds are divided in irrigation zones accounting for the spatial variability

of soil hydraulic properties (Gumiere et al., 2014). Based on the second criteria, the average WTD

should be less than 66 cm for minimizing sprinklers irrigation use.

2.3.3. Third criteria: Fast drainage

When the SWT just before a rainfall was higher than 7.0 kPa (WTD > 80 cm), the time after the

rainfall required to return to a value of 3.0 kPa (WTD = 40 cm) was close to zero (Figure 2.9).

Drainage was then fully efficient with no risk of hypoxic conditions in the root zone. When SWT

was less than 7.0 kPa (WTD < 80) just before a rainfall, the time required to drain was almost

linearly related to SWT for each individual rainfall event. The drier the soil before a rainfall, the

quicker the drainage.

For the particular rainfall event of 33 mm, when SWT was higher than 7.0 kPa, less than 2 h were

required to return to 3.0 kPa (Figure 2.10). However, 52 h were necessary to drain back to 3.0 kPa

when SWT was 3.9 kPa just before the rainfall; considering that this rainfall event occurred in two

phases, the SWT remained under 3.0 kPa for 65 consecutive hours. Hypoxic stress in the root zone

resulting from slow drainage can be harmful to the plants and reduce their productivity.

Since 40 mm of water are applied to protect the vines in a frost protection night, low values of SWT

before protection could result in extended period of hypoxic conditions, especially when frost

occurred on consecutive nights. Based on the third criteria, the water level in the canals should be

lowered to 80 cm below the beds surface when a rainfall or a frost is anticipated to avoid hypoxic

stress associated with SWT less than 3.0 kPa.

2.4. Conclusion

Sustainability in cranberry production can be enhanced by improving the performance of water

management. Water table control has the potential for increasing yield without decreasing quality,

minimizing the amount of water needed by the sprinkler system, and avoiding hypoxic stresses in

the rhizosphere. This study was conducted to determine the optimal water table depth (WTD) in

cranberry production when using water table control with sprinkler irrigation as additional

irrigation. Our results show that the final yield, the berry sugar content, the total number of berries,

the number of berries per upright, and the fruit set were maximized when the WTD was 60 cm.

Sprinkler water savings of 77% were obtained where the WTD was shallower than 66 cm. In order

to avoid hypoxic conditions due to poor drainage, the water level in the canals surrounding the beds

31

should be lowered to 80 cm when a rainfall or a frost protection irrigation is anticipated. All sides of

a block of beds must be surrounded by canals to ensure a uniform WTD and to avoid lateral

hydraulic gradients that could cause peripheral seepage losses. Further studies are needed to

determine the optimal water table control design (drain depth and drain spacing) to enhance

maintaining an optimal WTD and improve the drainage efficiency.

Figure 2.8. Soil Water Tension (SWT; solid lines) and manual readings of Water Table Depth (WTD; circles) at each site for 2013 and 2014. The vertical bars in the upper part of each graph represent irrigation events of 12 mm. The gray area indicates the hydric comfort zone (3.0 - 7.5 kPa).

32

Figure 2.9. Time required for the soil water tension (SWT) to return to a value of 3.0 kPa (WTD = 40 cm) after a major rainfall event as a function of the SWT just before the rainfall event.

Figure 2.10. Soil water tension (SWT) for a rainfall of 33 mm for different values of SWT just before the rainfall

2.5. Acknowledgements

The authors of this paper acknowledge the financial contribution of the Natural Sciences and

Engineering Research Council of Canada, Fonds de Recherche Nature et Technologies du Québec,

Nature Canneberge, Canneberges Bieler, Transport Gaston Nadeau, Hortau and the Scientific

Research and Experimental Development Tax Incentive Program of the Canada Revenue Agency

and Revenu Québec. We thank Jonathan Lafond, Benjamin Parys, and all the undergraduate

students who helped collecting the data.

0

10

20

30

40

50

60

3 4 5 6 7 8 9 10

Time (h) required for the SWT to return 

to 3.0 kPa after rainfall

SWT (kPa) before rainfall 

20 mm33 mm40 mm64 mm

Rainfall:

‐1,5

3,0

7,5

12,0

‐18 ‐12 ‐6 0 6 12 18 24 30 36 42 48 54

SWT (kPa)

Time (h) after the end of the rainfall event

3.9 5.0 5.1

5.2 7.0 8.1

End ofrainfall

SWT just before the rainfall (kPa):

33

2.6. References

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APCQ (Association des Producteurs de Canneberges du Québec). 2015. Statistiques de production. Available online: http://www.notrecanneberge.com/Industrie/Infos/statistiques.html (accessed on 21 May 2015).

Baumann, D.L., Workmaster, B.A., Kosola, K.R. 2005. ‘Ben Lear’ and ‘Stevens’ cranberry root and shoot growth response to soil water potential. HortScience. 40: 795–798.

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Birrenkott, B.A., Henson, C.A., Stang, E.J. 1991. Carbohydrate levels and the development of fruit in cranberry. J. Am. Soc. Hortic. Sci. 116: 174–178.

Bland, W.L., Loew, J.T., Norman, J.M. 1996. Evaporation from cranberry. Agric. For. Meteorol. 81: 1–12.

Brown, A.O., McNeil, J.N. 2006. Fruit production in cranberry (Ericaceae: Vaccinium macrocarpon): A bet-hedging strategy to optimize reproductive effort. Am. J. Bot. 93: 910–916.

Caron, J., Pepin, S., Bonin, S. 2016. Determination of irrigation set points for cranberries from soil and plant-based measurements. Can. J. Soil Sci. 96: 37-50.

Eaton, G. W., Shawa, A., Bowen, P.A. 1983. Production of individual cranberry uprights in Washington and British Columbia. Sci. Hortic. 20:179-184.

Eck, P. 1976. Cranberry growth and production in relation to water table depth. J. Am. Soc. Hortic. Sci. 101: 544–546.

Eck, P. 1990. The American Cranberry, Rutgers University Press, New Brunswick, NJ, USA.

Elmi, A., Madramootoo, C., Handyside, P., Dodds, G. 2010. Water requirements and subirrigation technology design criteria for cranberry production in Quebec, Canada. Can. Biosyst. Eng. 52: 1–8.

Evans, R.O., Gilliam, J.W., Skaggs, R.W. 2015. Controlled Drainage Management Guidelines for Improving Drainage Water Quality. Available online: http://www.bae.ncsu.edu/programs/extension/evans/ag443.html (accessed on 21 May 2015).

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Fuleki, T., Francis, F.J. 1968. Quantitative methods for anthocyanin: Extraction and determination of total anthocyanin in cranberries. J. Food Sci. 33: 72–77.

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Gumiere, S.J., Lafond, J.A., Hallema, D.W., Périard, Y., Caron, J., Gallichand, J. 2014. Mapping soil hydraulic conductivity and matric potential for water management of cranberry: Characterisation and spatial interpolation methods. Biosyst. Eng. 128: 29–40.

Hagidimitriou, M., Roper, T.R. 1994. Seasonal changes in non-structural carbohydrates in cranberry. J. Am. Soc. Hortic. Sci. 119: 1029–1033.

Hall, I.V. 1971. Cranberry growth as related to water levels in the soils. Can. J. Plant Sci. 51: 237–238.

Handyside, P. 2003. Water Table Management for Cranberry Production on Sandy Soil and Peat Soils in Québec. Master’s Thesis, McGill University, Montréal, QC, Canada.

Hattendorf, M.J., Davenport, J.R. 1996. Cranberry evapotranspiration. HortScience. 31: 334–337.

Kahlown, M.A., Ashraf, M., Zia-ul-Haq. 2005. Effect of shallow groundwater table on crop water requirements and crop yields. Agric. Water Manag. 76: 24–35.

Lanari, V., Palliotti, A., Sabbatini, P. Stanley Howell, G. 2014. Optimizing deficit irrigation strategies to manage vine performance and fruit composition of field-grown ‘Sangiovese’ (Vitis vinifera L.) grapevines. Sci. Hortic. 179: 239–247.

Laurent, T. 2014. Réponse de la canneberge (Vaccinium macrocarpon Ait.) à l’aération du sol. Master’s Thesis, Université Laval, Québec, QC, Canada.

Madramootoo, C.A., Dodds, G.T., Papadopoulos, A. 1993. Agronomic and environmental benefits of water-table management. J. Irrig. Drain. Eng. 119: 1052–1065.

Madramootoo, C.A., Helwig, T.G., Dodds, G.T. 2001. Managing water tables to improve drainage water quality in Quebec, Canada. Trans. Am. Soc. Eng. 44: 1511–1519.

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Marchand, S., Parent, S.-E., Deland, J.-P., Parent, L.-E. 2013. Nutrient signature of Quebec (Canada) cranberry (Vaccinium macrocarpon Ait.). Rev. Bras. Frutic. 35: 292–304.

Nemon, N.A., von Hoyningen Huene, B., Gallichand, J., Broughton, R.S. 1987. Subsurface irrigation and drainage on sandy soil in Southern Quebec. Can. Agric. Eng. 29: 137–142.

Nosetto, M.D., Jobbágy, E.G., Jackson, R.G., Sznaider, G.A. 2009. Reciprocal influence of crops and shallow ground water in sandy landscapes of the Inland Pampas. Fields Crop Res. 113: 138–148.

Pelletier, V., Gallichand, J., Caron, J., Jutras, S., Marchand, S. 2015. Critical irrigation threshold and cranberry yield components. Agric. Water Manag. 148: 106–112.

Pelletier, V., Gallichand, J., Caron, J. 2013. Effects of soil water potential threshold for irrigation on cranberry yield and water productivity. Trans. Am. Soc. Agric. Biol. Eng. 56: 1325–1332.

Pitts, D.J., Tsai, Y.J., Myhre, D.L., Anderson, D.L., Shih, S.F. 1993. Influence of water table depth on sugarcane grown in sandy soils in Florida. Trans. Am. Soc. Eng. 36: 777–782.

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Samson, M.-E., Caron, J., Fortin, J. 2013. Impacts of low water potential on soil salinity and its effects on cranberry development. In Proceedings of North American Cranberry Researchers and Extension Workers Conference, Quebec City, QC, Canada, 25–28 August 2013.

Sandler, H.A., DeMoranville, C.J., Lampinen, B. 2004. Cranberry irrigation management. Available online: http://www.umass.edu/cranberry/downloads/Irrigation.pdf (accessed on 21 May 2015).

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36

CHAPITRE 3 Cranberry Gas Exchange under Short-term Hypoxic Soil Conditions

Vincent Pelletier 1, Steeve Pepin1, Thomas Laurent1, Jacques Gallichand 1, and Jean Caron 1

1Département des Sols et de Génie Agroalimentaire, Université Laval, 2425 rue de l’Agriculture, Université Laval, Québec City, Québec, Canada, G1V 0A6;

37

Résumé. Des canneberges ont été cultivées en cabinet de croissance sous conditions contrôlées afin

de déterminer l’effet de la saturation du sol sur les échanges gazeux de la canneberge lors de trois

stades de développement ainsi que pour investiguer le temps de récupération après drainage. La

photosynthèse a diminué de 28% après le premier jour en conditions saturées lors du stade

d’élongation des bourgeons pour atteindre une diminution de 46% après le cinquième jour. Pendant

le stade de la floraison, la réduction de la photosynthèse est devenue significative après le

cinquième jour de saturation tandis qu’aucune réduction n’a été mesurée lors du stade de

développement des fruits. Puisqu’après le cinquième jour de saturation la conductance stomatique a

diminué de 68% lors du stade d’élongation des bourgeons et de 45% lors du stade de floraison, la

diminution de photosynthèse observée lors de ces périodes peut être en partie attribuée à des

limitations stomatiques. Lors du stade d’élongation des bourgeons, le taux de photosynthèse des

feuilles du traitement saturé est demeuré inférieur à celui des feuilles du traitement non-saturé

pendant plus de 10 jours après que l’eau fut évacuée par drainage. Nos résultats ont démontré que

les échanges gazeux de la canneberge peuvent être altérés par des conditions de sol hypoxiques et

suggèrent qu’un drainage adéquat ou qu’un contrôle de la profondeur de la nappe est nécessaire afin

d’en éviter les conséquences négatives sur les rendements de la canneberge.

38

Abstract. Cranberries were grown under controlled environmental conditions to determine the

effects of soil waterlogging on cranberry gas exchange in three growth stages and to investigate the

recovery time following waterlogging. Photosynthesis declined by 28% after the 1st day of

waterlogging at the bud elongation stage and was 46% lower after the 5th day. At the flowering

stage, the reduction in photosynthesis started to be significant only after the 5th day while no

reduction was observed at the fruit development stage. Stomatal limitations were responsible, in

part, for the observed decrease in photosynthesis since stomatal conductance declined by 68% and

45% after the 5th day of waterlogging during bud elongation and flowering, respectively. After

water drained away in the saturated treatments, leaf photosynthesis remained lower than in the

unsaturated control treatment for one to more than 10 days at the bud elongation stage. Our results

demonstrate that short-term hypoxic soil conditions can alter cranberry gas exchange depending on

plant growth stage and suggest that adequate drainage or control of the water table depth is required

to avoid the negative effects of soil waterlogging on cranberry yield.

39

3.1. Introduction

The cultivated cranberry (Vaccinium macrocarpon Ait.) is a perennial plant native from North

America (Eck, 1990). Its productivity is maximized when soil water potential in the root zone (at

~10 cm depth) is maintained between -3.0 and -7.5 kPa (Pelletier et al., 2013; Caron et al., 2016;

Laurent, 2015) and growers can use overhead irrigation to avoid water stress when the lower

threshold is reached. Most of the cranberry beds are equipped with drain tiles for removing excess

water after rainfall or sprinkler frost protection, but drainage systems can also be used for

subirrigation where the water table depth is controlled by adding water in drain tiles. Historically,

cranberries were grown under wet conditions with shallow water tables around 23-38 cm below the

ground surface (Eck, 1990), but there is evidence that higher yields can be attained when the water

table is about 60 cm deep (Pelletier et al., 2015). While drainage problems could induce significant

yield limitation (Baumann et al., 2005), the time to remove the excess of water greatly depends on

the water table depth prior to rainfall (Pelletier et al., 2015). Recent improvements in water

management, the outcome of efforts at promoting the benefits of drier soil conditions, could explain

in part the yield increases observed in recent years in the province of Québec (Canada). Indeed, the

average yield in conventional production systems increased by 38% over the last decade (from

24000 kg ha-1 in 2004 to 33000 kg ha-1 in 2014) (APCQ, 2015).

A decline in photosynthesis is one of the first physiological responses to soil waterlogging (Liao

and Lin, 2001). Poor aeration in the root zone generally leads to a reduction in root cellular

respiration and permeability, followed by a decline in water absorption (Bhattarai et al., 2005).

Stomata then close gradually, transpiration is reduced, and carbohydrate translocation from leaves

to roots is inhibited (Liao and Lin, 2001). The extension of root axes can be severely reduced as a

result of ethylene production under anaerobic conditions resulting in injury to the plant (Smith and

Restall, 1971). It has been shown in many crops, such as blueberries (Davies and Flore, 1986a),

cherries (Beckman et al., 1992), and sunflowers (Grassini et al., 2007), that leaf gas exchange is

affected by the lack of oxygen in the rhizosphere. Depending on the growth stage at which soil

waterlogging occurs, such reduction in CO2 assimilation may reduce the number of fruiting

uprights, number of flowers, fruit set and fruit size (Kozlowski, 1997). Hence, lower carbon

assimilation under saturated soil conditions could reduce plant growth and lead to significant yield

loss. The magnitude of these impacts will depend on the time required to recover and return to pre-

flooding values when waterlogging ends. However, although the reduction in plant gas exchange

under soil waterlogging and the recovery time are species dependent (Kozlowski, 1997), little is

known about these relationships in cranberry production– yet essential to improve the design of

40

drainage systems and avoid yield limitations caused by inadequate drainage. Therefore, the

objectives of the present study were to determine the effect of soil waterlogging duration on

cranberry gas exchange and to investigate the recovery time after removing the excess water.

3.2. Materials and Methods

The experiments were carried out in an 18 m3 controlled growth chamber (BDW80, Conviron,

Winnipeg, Manitoba, Canada) located at Université Laval in Québec City, Canada (lat. 46°46' N,

long. 71°16' W). Mature ‘Stevens’ cranberry plants were collected as 0.06 m2 square mats of vines

from a fine sand field in October and grown in 0.27 m3 containers filled with fine to medium sand.

Particular attention was paid to avoid damaging the roots and shoots when removing each mat from

the soil. Plants were overwintered in the dark at air temperature of 4 °C and relative humidity (RH)

of 80% for 2880 h, satisfying the recommended time of 2500 h (Eady and Eaton, 1972). For the

first week of breaking dormancy (d=1 to d=7), temperature was set to 15 °C from 1300 to 1800 hr

and to 6 °C from 0100 to 0500 hr with constant hourly steps between these periods. RH was

controlled at 50% during the day and 80% during the night, following a time course similar to

temperature. From d=8 to d=14, the temperature was set to 21 °C day/11 °C night and from d=15 to

d=147, to 25 °C day/16 °C night. Plants were exposed to a 13-h photoperiod during breaking

dormancy and 15-h during the growing season. Metal halide high-intensity discharge lamps (n=33,

400 W each) were used to provide a photosynthetic photon flux density of 600 µmol·m-2·s-1 at plant

level, corresponding to light-saturated conditions for cranberry (Kumudini, 2004). Each

experimental unit (EU) of 0.27 m3 was seated in a 0.76 m3 container. Water was added in the large

container and small holes were drilled in the bottom of the small container to ensure water entering

into the soil by upward flux. A Mariotte bottle was connected to the large container to replace the

water lost by evapotranspiration (Soppe and Ayars, 2003). Mariotte bottles were filled each week

for maintaining a constant water table depth. Except for fertilization, no water was added to the soil

surface. Fertilizers were applied at 10%, 50%, and 100% of flowering for a total dose of 40 kg ha-1

N, 60 kg ha-1 P and 125 kg ha-1 K. Nutrients were mixed with 250 ml of water per EU and manually

applied with a commercial watering can. Flowers were hand-pollinated each day with a small

paintbrush from d=44 to d=65. This resulted in fruit set (~40%) similar to that observed in the field

(see Pelletier et al., 2015), with no significant difference among experimental units.

Treatments consisted of soil waterlogging time varying from 0 (Control) to 5 d (1-day, 2-day, 3-

day, and 5-day) and were applied at three different growth stages: bud elongation (d=24 after

41

dormancy), flowering (d=51), and fruit development (d=77; i.e. ~2 weeks after fruit set). Soil in the

control treatment was never waterlogged. To apply the saturation treatments, the water level in the

0.76 m3 containers was increased until the soil was completely saturated by capillary rise, as

evidenced by a thin layer of water at the soil surface. At the end of each saturation treatment, the

water in the large containers was removed. Due to the high saturated hydraulic conductivity of the

soil and the absence of restrictive constraints, water drained away in less than 30 minutes following

the treatment period.

Measurements of photosynthesis (Pn), stomatal conductance (gs), and transpiration (E) were

performed each day using the same uprights between 1300 and 1600 hr on the day before treatments

application and for the next 12 d (except for the 6th, 8th, 10th and 11th d) using a portable

photosynthesis system (LI-6400XT, Li-Cor, Lincoln, Nebraska, USA) equipped with a 6 cm2

chamber and a red/blue LED light source (6400-02B, Li-Cor). Leaf gas exchange was measured up

to seven days after the termination of the longest saturation treatment to allow estimation of the

recovery time. A different set of uprights was selected at each development stage. One-year-old

leaves were used at the bud elongation stage while current year foliage was used at the flowering

and fruit development stages. Leaves were first acclimated under 800 µmol·m-2·s-1 PPFD, 25 ± 1 °C

leaf temperature, 400 µmol·mol-1 leaf chamber air CO2, 400 µmol·s-1 air flow rate, and gas

exchange variables (Pn, gs, E) were recorded once they had reached steady state. The leaf-to-air

vapor pressure deficit (VPDl) was maintained at 1.2 ± 0.1 kPa during measurements. Because of the

difficulty to ensure a good contact between the foliage and the leaf thermocouple, the latter was

positioned to measure air temperature instead of leaf temperature and the energy balance method

was used for estimating leaf temperature and calculating related gas exchange parameters. After

measurements, leaves were collected and digitized with a flatbed scanner to determine leaf area

using the ImageJ software (W.S. Rasband, U. S. National Institutes of Health, Bethesda, MD) and

measured gas exchange values were adjusted accordingly.

The experimental setup was a randomized complete block design with four replicates by treatment

for a total of 20 experimental units. Differences between the saturated and control treatments were

analyzed using the contrast statement of the PROC MIXED of SAS 9.3 (SAS Institute, Cary, North

Carolina, USA).

42

3.3. Results

The sensitivity of cranberry plants to hypoxic soil conditions depended on crop stage. At the bud

elongation stage, there was a rapid decline in Pn when vines were exposed to soil saturation. Indeed,

Pn was significantly decreased by 28% after the 1st day of soil saturation compared with the control

treatment, and the overall difference was 46% after 5 d of treatment (Figure 3.1a). In contrast, the

responses of leaf photosynthesis to saturated soil conditions were slower during the flowering stage.

There was a gradual decline in Pn as the number of days with saturated soil conditions increased but

Pn started to be significantly lower than the control only on the 5th day of saturation (-34%).

Cranberry vines were not sensitive to short-term soil saturation during the fruit development stage,

as no significant difference was observed between treatments, even 5 days after saturating the soil.

The reduction of Pn under hypoxic soil conditions could be partly due to stomatal limitation. Indeed,

mean intercellular CO2 concentration (Ci) declined from 320 µmol CO2 mol-1 in control plants to

283 µmol CO2 mol-1 in treated vines after 5 d of saturation at the bud elongation stage. Moreover, gs

declined significantly after 3 d of exposure to soil saturation during bud elongation and flowering

but remained similar to control values during fruit development (Figure 3.1b). The overall decrease

in gs after 5 d of saturation was 68% during bud elongation and 45% during flowering. As VPDl

was controlled at a constant value throughout measurements, the changes in leaf transpiration

attributable to saturated soil conditions were similar to those in gs (data not shown).

The Pn and gs values measured after drainage were normalized relative to those observed on the 1st

day of measurement (d=0) in order to compare the time required for cranberry uprights exposed to 1

to 5 d of soil saturation to return to Pn and gs values of the control treatment. During bud elongation,

Pn of vines that had been waterlogged for 1 d was similar to that of control vines on the 2nd day after

drainage occurred (Figure 3.2a). In contrast, it took between 4 to more than 10 d for cranberry

plants exposed to longer saturation times to reach Pn values of the controls (Figure 3.2b). Indeed, Pn

in the 2-day saturation treatment was still 27% lower than in the control treatment after 10 d of

recovery (Figure 3.2b) and about 40% lower in the 5-day treatment after 7 d of recovery (Figure

3.2d), thereby suggesting that the full recovery time of CO2 assimilation is longer than 7–10 d in

severely waterlogged cranberry vines. Interestingly, at the flowering stage, Pn in treatments that

were saturated between 1 and 3 d (Figure 3.2a-c) returned to values similar to those of the control

treatment on the 1st day after drainage. However, there was a trend in Pn values of control plants to

increase faster over time, resulting in a significant difference between treated and control vines on

day 6 to 8 after drainage, depending on the duration of the saturation treatment (Figure 3.2a-c). In

the 5-day treatment, Pn remained lower than the control treatment at least seven days after drainage

43

(Figure 3.2d). At the fruit development stage, while the differences in Pn between treated and

control vines were significant on a few sampling days, they were relatively small, which is

consistent with soil saturation having no effect on Pn during fruit development (see Figure 3.1).

Overall, there were no significant differences between gs of the control and saturation treatments,

except at the bud elongation stage for the 2-day and 5-day treatment only (data not shown).

Bud elongation Flowering Fruit development A

B

Bud elongation Flowering Fruit development

Figure 3.1. Changes in (a) photosynthesis (Pn) and (b) stomatal conductance (gs) as a function of the number of days with saturated soil conditions at the stage of bud elongation, flowering, and fruit development. Sixteen experimental units were saturated for one to five days (1-day, 2-day, 3-day, 5-day; n=4 per treatment) and four control units were sampled each day. Day 0 corresponded to the day prior to the saturation treatments and four experimental units were drained after 1, 2, 3 and 5 days. Significance levels are: p < 0.001 (***), p < 0.01 (**), p < 0.05 (*), non-significant (NS). Means and 95% confidence intervals are indicated.

0

2

4

6

8

10

12

‐1 0 1 2 3 4 5 6

Pn(µmol ∙ CO2m

‐2s‐1)

Days with saturated soil

Control Saturated

NS       *       **      *        *       ** 

‐1 0 1 2 3 4 5 6

Days with saturated soil

NS     NS     NS     NS      NS       * 

‐1 0 1 2 3 4 5 6

Days with saturated soil

NS     NS     NS     NS      NS     NS 

0

0,1

0,2

0,3

‐1 0 1 2 3 4 5 6

g s(m

ol ∙ H

2O m

‐2s‐1)

Days with saturated soil

Control Saturated

NS     NS      *         *        *      **

‐1 0 1 2 3 4 5 6

Days with saturated soil

NS     NS     NS       *        * *

‐1 0 1 2 3 4 5 6

Days with saturated soil

NS    NS     NS      NS     NS    NS 

44

Bud elongation Flowering Fruit development A

B

C

D

Bud elongation Flowering Fruit development

Figure 3.2. Photosynthesis as a function of the number of days after drainage at the stage of bud elongation, flowering, and fruit development for treatment with (a) 1, (b) 2, (c) 3, and (d) 5 consecutive day of soil saturation. Values were standardized according to the first day of measurement. Significance levels are: p < 0.001 (***), p < 0.01 (**), p < 0.05 (*), non-significant (NS). Means and 95% confidence intervals are indicated.

0%

50%

100%

150%

200%

0 1 2 3 4 5 6 7 8 9 101112Days after drainage

Control Saturated

*** NS  NS   NS        NS         NS               NS

0 1 2 3 4 5 6 7 8 9 101112

Days after drainage

NS  NS  NS  NS         NS         *                   *

0 1 2 3 4 5 6 7 8 9 101112

Days after drainage

NS  NS  NS    *         NS          NS                **

0%

50%

100%

150%

200%

0 1 2 3 4 5 6 7 8 9 10 11Days after drainage

Control Saturated

*** *** ***          **         *** **

0 1 2 3 4 5 6 7 8 9 10 11

Days after drainage

NS   NS   NS         NS            *                    **     

0 1 2 3 4 5 6 7 8 9 10 11

Days after drainage

NS   NS   NS          NS           NS                 NS

0%

50%

100%

150%

200%

0 1 2 3 4 5 6 7 8 9 10

Days after drainage

Control Saturated

*      *             NS             *                     NS  

0 1 2 3 4 5 6 7 8 9 10

Days after drainage

NS    NS           NS             *                       *     

0 1 2 3 4 5 6 7 8 9 10

Days after drainage

*       *             NS           NS                     NS

0%

50%

100%

150%

200%

1 2 3 4 5 6 7 8

Days after drainage

Control Saturated

***                 ***                             ***

1 2 3 4 5 6 7 8

Days after drainage

*                      *                                  *

1 2 3 4 5 6 7 8

Days after drainage

NS                      *                                NS            

45

3.4. Discussion

Photosynthetic capacity is often inhibited in flooding-intolerant plants exposed to saturated soil

conditions (Liao and Lin, 2001). Our results demonstrate that cranberry is sensitive to waterlogging.

Based on long-term weekly measurements, Laurent (2015) also observed a significant reduction in

Pn and gs of cranberry after the first week of waterlogging and suggested that photosynthesis

inhibition could occur sooner. In this study, gas exchange measurements were performed on a daily

basis and a significant decline in Pn was found after the first day of waterlogging (Figure 3.1a). Of

course, such reduction of photosynthesis may have occurred earlier than we observed, i.e. within

hours of saturating the soil. Because the decrease in gs occurred 2 d after the reductions in Pn (see b)

our results suggest that soil saturation induced non-stomatal limitations of photosynthesis. It has

indeed been shown that lower Pn in the first days after waterlogging could be associated with a

reduction of RuBP regeneration (Bradford, 1983), a decrease in carboxylation efficiency

(Fernandez, 2006), or a decrease in the chlorophyll content of leaves (Insausti and Gorjón, 2013).

For poorly adapted species, a major constraint due to the excess of water is an inadequate supply of

oxygen to root tissues, the diffusion of oxygen through water being 104 times slower than in the air

(Jackson and Colmer, 2005). The lack of aeration in the rhizosphere may induce different

physiological responses that lower plant CO2 assimilation and could impact crop yield.

This study is the first to examine the short-term effects of soil waterlogging in cranberries, however,

similar results have been reported for other Vaccinium species. For instance, photosynthetic carbon

assimilation of rabbiteye blueberry (Vaccinium ashei Reade) declined by 36% after 1 d of soil

saturation and by 62% after the 4th consecutive day of saturation and was associated in part with

stomatal limitations (Davies and Flore, 1986a). In highbush blueberries (Vaccinium corymbosum

L.), a decrease in stomatal conductance brought about by a 56% reduction in root hydraulic

conductivity resulted in lower carbon assimilation within 1-2 days of flooding (Davies and Flore,

1986b). Similar results were also reported for other crops, such as in sour cherries (Prunus cerasus

L.), where carbon assimilation was affected less than 12 h after flooding and declined by 68% over

5 d (Beckman et al., 1992).

Gas exchange was negatively affected by soil waterlogging during bud elongation and flowering,

but not during fruit development (Figure 3.1). The effects of waterlogging varying with plant

ontogeny are species specific (Kozlowski, 1997). For example, the early stages of maize were also

found to be the most susceptible to an excess of water (Zaidi et al., 2004). In contrast, four flooding

days occurring eight days before snap beans (Phaseolus vulgaris L.) flowering resulted in 96% of

46

plant survival and a similar harvest index than the control treatment. However, when flowering

occurred 8 d after flooding, only 4% of the plants survived and there was no pods to harvest

(Lakitan et al., 1992). Because the same plants were used for all waterlogging treatment periods in

our experiment, a carry-over effect could have masked the growth stage effect. This has been

observed in other crops such as in wheat where waterlogging before anthesis was found to indeed

enhance tolerance after anthesis by increasing Pn, gs and E (Li et al., 2011). In any case,

waterlogging affected cranberry gas exchange at least in the early development stage.

Flooding is commonly used as a pest management tool in cranberries production. It has been

demonstrated that a fall flood is efficient to limit cranberry fruitworm emergence and reduce

dewberry weed (DeMoranville et al., 2005) while a 10-d flood during fruit set reduced the overall

weed coverage (Sandler and Mason, 2010). Lower carbohydrate accumulation in cranberry uprights

is a direct consequence of spring flood (Vanden Heuvel and Goffinet, 2008). Though vines were not

covered by water in our experiment, the reduction in Pn observed here suggests that soil saturation is

sufficient to impact plant growth and fruit development. It is important to note that flooding used as

an integrated pest management tool may be economically beneficial in comparison with pesticide

applications, however there is a need for better tools that avoid the detrimental consequences of

flooding on final crop yield. Frost protection by overhead irrigation can also lead to soil saturation

(Perry, 1998). Consecutive nights of frost protection may result in several days of soil waterlogging

when the water table is too shallow. Although frost protection by irrigation is essential to prevent

damage to the crop, it is recommended to lower the water table before irrigation to avoid saturation

of the soil for extended periods and thereby limit crop loss (Pelletier et al., 2015). Automated

intermittent irrigation during frost protection (i.e. the cycling of irrigation) is another method to

limit soil waterlogging and the concomitant impairment of cranberry yield (P. Jeranyama,

unpublished data).

In general, Pn in the saturated treatments did not return to control values immediately after drainage.

It thus appears that non-stomatal limitations of photosynthesis were more important than stomatal

limitations and have prevailed through recovery. Indeed, Ci values were only 11% lower after 5 d of

saturation and were similar with control for all treatments after drainage at bud elongation while no

differences were observed during flowering and fruit development. In some cases, it took more than

10 d to recover the gas exchange rates of controls, in line with results for other Vaccinium species.

In highbush blueberries (V. corymbosum L.), the recovery of gs to pre-flood values required 18 d

after 24 d of flooding whereas more than 18 d were necessary in rabbit-eye blueberries (V. ashei

Reade) (Davies and Flore, 1986a).

47

According to our data, waterlogging should be avoided in cranberry production especially during

early development. Efficient subsurface drainage is an excellent approach to controlling soil

saturation. With predicted increases in rainfall intensity and frequency due to climate change and

since actual drainage systems allow water to be removed in more than 24 h after precipitation in

some cases (Pelletier et al., 2015), further work should focus on implementation of the drainage

system design.

3.5. Conclusion

In summary, Pn was significantly reduced after 1 d of soil waterlogging at the bud elongation stage

and after 5 d at the flowering stage. After water drained away, the recovery time was dependent of

the waterlogging duration but varied from 1 d to more than 10 d. Drainage is therefore an important

management practice to avoid the negative effects of soil waterlogging on cranberry gas exchange.

3.6. Acknowledgements

The authors of this paper acknowledge the financial contribution of the Natural Sciences and

Engineering Research Council of Canada, Fonds de Recherche Nature et Technologies du Québec,

Nature Canneberge, Canneberges Bieler, Transport Gaston Nadeau, Hortau and the Scientific

Research and Experimental Development Tax Incentive Program of the Canada Revenue Agency

and Revenu Québec. We thank Jonathan Lafond and Benjamin Parys for providing helpful

comments on a previous version of the manuscript.

48

3.7. References

APCQ (Association des Producteurs de Canneberges du Québec). 2015. Statistiques de production. Available online: http://www.notrecanneberge.com/Industrie/Infos/statistiques.html (accessed on 17 August 2015).

Baumann, D.L., Workmaster, B.A., Kosola, K.R. 2005. ‘Ben Lear’ and ‘Stevens’ cranberry root and shoot growth response to soil water potential. HortScience. 40: 795-798.

Bhattarai, S.P., Su, N., Midmore, D.J. 2005. Oxygation unlocks yield potentials of crops in oxygen-limited soil environments. Adv. Agron. 88: 313-377.

Beckman, T.G., Perry, R.L. Flore, J.A. 1992. Short-term flooding affects gas exchange characteristics of containerized sour cherry trees. HortScience. 27: 1297-1301.

Bradford, K.J. 1983. Effects of soil flooding on leaf gas exchange of tomato plants. Plant Physiol. 73: 475-479.

Caron, J., Pepin, S., Bonin, S. 2016. Determination of irrigation setpoints for cranberries from soil- and plant-based measurements. Can. J. Soil Sci. 96: 37-50.

Davies, F.S., Flore, J.A. 1986a. Short-term flooding effects on gas exchange and quantum yield of rabbiteye blueberry (Vaccinium ashei Reade). Plant Physiol. 81: 289-292.

Davies, F.S., Flore, J.A. 1986b. Flooding, gas exchange and hydraulic conductivity of highbush blueberry. Physiol. Plant. 67: 545-551.

DeMoranville, C.J., Sandler, H.A., Shumaker, D.E., Averill, A.L., Caruso, F.L., Sylvia, M.M., Pober, D.M. 2005. Flooding for management of cranberry fruitworm (Acrobasis vaccinii) and dewberry (Rubus hispidus) in Massachusetts cranberry production. Crop Protection. 24: 999-1006.

Eady, F.C., Eaton, G.W. 1972. Effects of chilling during dormancy on development of the terminal bud of the cranberry. Can. J. Plant Sci. 52: 273-279.

Eck, P. 1990. The American cranberry. Rutgers University Press, New Brunswick, NJ.

Fernandez, M.D. 2006. Changes in photosynthesis and fluorescence in response to flooding in emerged and submerged leaves of Pouteria orinocoensis. Photosynthetica. 44: 32-38.

Grassini, P., Indaco, G.V., López Pereira, M., Hall, A.J., Trápani, N. 2007. Responses to short-term waterlogging during grain filling in sunflower. Field Crops Res. 101: 352-363.

Insausti, P., Gorjón, S. 2013. Floods affect physiological and growth variables of peach trees (Prunus persica (L.) Batsch), as well as the postharvest behavior of fruits. Scientia Hort. 152: 56-60.

Jackson, M.B. Colmer, T.D. 2005. Response and adaptation by plants to flooding stress. Ann. Bot. 96: 501-506.

Kozlowski, T.T. 1997. Responses of woody plants to flooding and salinity. Tree Physiology Monograph No. 1. Heron Publishing, Victoria (Canada).

49

Kumudini, S. 2004. Effect of radiation and temperature on cranberry photosynthesis and characterization of diurnal change in photosynthesis. J. Amer. Soc. Hort. Sci. 129: 106-11.

Lakitan, B., Wolfe, D.W., Zobel, R.W. 1992. Flooding affects snap bean yield and genotypic variation in leaf gas exchange and root growth response. J. Amer. Soc. Hort. Sci. 117: 711-716.

Laurent, T. 2015. Réponse de la canneberge (Vaccinium macrocarpon Ait.) à l’aération du sol. MS Thesis, Université Laval, Quebec City.

Li, C., Jiang, D., Wollenweber, B., Li, Y., Dai, T., Cao, W. 2011. Waterlogging pretreatment during vegetative growth improves tolerance to waterlogging after anthesis in wheat. Plant Sci. 180: 672-678.

Liao, C.-A. Lin, C.-H. 2001. Physiological adaptation of crop plants to flooding stress. Proc. Nat. Sci. Council. 25: 148-257.

Pelletier, V., Gallichand, J., Caron, J. 2013. Effect of soil water tension threshold for irrigation on cranberry yield and water productivity. Trans. Amer. Soc. Agr. Biol. Eng. 56: 1325-1332.

Pelletier, V., Gallichand, J., Gumiere, S., Pepin, S., Caron, J. 2015. Water table control for increasing yields and water saving in cranberry production. Sustainability. 7: 10602-10619.

Perry, K.B. 1998. Basics of frost and freeze protection for horticultural crops. HortTechnology. 8: 10-15.

Sandler, H.A., Mason, J. 2010. Flooding to manage codder (Cuscuta gronovii) and broad-leaved weed species in cranberry: An innovative use of a traditional strategy. Renewable Agr. Food Systems. 25: 257-262.

Smith, K.A., Restall, S.W.F. 1971. The occurrence of ethylene in anaerobic soil. J. Soil Sci. 22: 430-443.

Soppe, R.W.O., Ayars, J.E. 2003. Characterizing ground water use by safflower using weighing lysimeters. Agr. Water Manage. 60: 59-71.

Vanden Heuvel, J.E. Goffinet, M.C. 2008. The effects of flood initiation timing and water temperature during flooding on non-structural carbohydrates concentration and anatomy of cranberry. HortScience. 43: 338-345.

Zaidi, P.H., Rafique, S., Rai, P.K., Singh, N.N., Srinivasan, G. 2004. Tolerance to excess moisture in maize (Zea mays L.): susceptible crop stages and identification of tolerant genotypes. Field Crops Res. 90: 189-202.

50

CHAPITRE 4 Impact of Drainage Problems on Cranberry Yield: Two Case Studies

Vincent Pelletier1, Jacques Gallichand1, Silvio Gumiere1 and Jean Caron1

1Département des sols et de génie agroalimentaire, Université Laval, 2425 rue de l’Agriculture, Université Laval, Québec City, Québec, Canada, G1V 0A6;

51

Résumé. L’impact de deux problèmes de drainage sur le rendement de la canneberge a été

investigué. Dans le premier cas, le rendement a diminué de 39% dû au colmatage des drains tandis

que dans le deuxième cas, une mauvaise conception de l’exutoire de drains a résulté en une baisse

de rendement de 25%. Les correctifs apportés ont fait disparaître cette baisse l’année suivante.

52

Abstract. The impact of two drainage problems on cranberry yield was investigated. In the first

case, a yield decline of 39% was measured for cranberries growing over clogged drains and, in the

second case, an inadequate design of the drainage outlet was associated with a 25% yield reduction.

This yield decrease vanished the following year after redesigning the outlet.

53

4.1. Introduction

Ten-cm diameter corrugated plastic drain pipes are often used for controlling the water table depth

in cranberry production. Because recent work identified cranberry as non-tolerant to hypoxic

conditions, the drainage system must be fully effective. Pelletier et al. (2016) observed that when

the soil was saturated early in the growing season, photosynthesis declined after only one day of

waterlogging. Also, Laurent (2015) showed that prolonged periods of hypoxic conditions (soil

water potential (SWP) > -3.0 kPa) lead to a decline of plant productivity.

Drainage problems are an important factor limiting cranberry yield (Baumann et al., 2005). Poor

design of the drainage system related to inappropriate drain depth or spacing and clogged drain

pipes are two of the main problems encountered in agricultural production. Mineral sedimentation

(Gallichand and Lagacé, 1987) or sludge deposition associated with bacterial activity in drain pipes

(Ford, 1979) considerably reduce water entry into drain pipes. Sludge depositions generally contain

organic matter (2 to 50% dry wt.) and form red to tan filamentous masses when combined to iron

ochre, black gelatinous deposits when combined to manganese, and white to yellow stringy masses

when combined to sulfur (Ford, 1993). In this paper, two case studies were investigated for

characterizing the yield losses associated with drainage problems in cranberry production in Québec

region.

4.2. Case study #1

In the first case, a grower reported, by the end of May 2011, that organic cranberries in half a bed

cropped with the Stevens variety were yet dormant (red vines) lagging behind the other half bed,

where cranberries were active (green vines). In this bed (525 m long and 54 m wide), there was a

drainage outlet (90 cm depth) at each end and the highest point of the four drain pipes (60 cm

depth) was located in the middle of the bed; the subsurface drainage system was therefore cone-

shaped. By digging a soil profile, it was rapidly observed that the sandy soil was saturated under the

red vines section, but not under the green vines section, and drain pipes were suspected to be

clogged in that section. On June 7, chimneys were connected to drain pipes in the middle of the bed

and a cleaning system used for removing the clogging material. The cleaning system consisted of a

2.5-cm diameter flexible hose inserted into the chimney, connected to a 3.75 kW gasoline pump

operated at 300 kPa and delivering 35 m3 h-1 of water. The water leaving the drain outlet was black

and contained clumps of clogging material. These swollen masses smelt bad, were gelatinous and

54

some masses were white to yellow with tan tinges while some were red to tan with black tinges

(Figure 4.1). After cleaning, red to tan deposits were found in some of the drain perforations, but

not at the outer surface of the synthetic drain envelope. The red vines slowly turned to green three

weeks after cleaning, but some died (Figure 4.2). Before cleaning the drains, the soil solution was

sampled (n=3) for Mn and Fe2+ analysed with the color disk method (model MN-5 and IR-20; Hach

Company; Loveland, Colorado). The clogging material was also sampled (n=3) for measuring the

organic matter content after burning in a muffle furnace at 550°C. At the end of the growing season,

yield samples (n=25; 929 cm2/sample) equally distributed in each of the two sections of the bed

were collected. The yield difference between the two sections was analysed using the GLM

function of R (R Foundation for Statistical Computing, Vienna, Austria).

Figure 4.1. The swollen masses found at the drain outlet after pumping water at low operating pressure (300 kPa) in drain pipes for washing.

Figure 4.2. Monitoring the development of cranberries growing over drain pipes clogged with swollen masses from June 7 to August 17 2012. Drain pipes were washed on June 7.

55

Cranberries growing over the clogged drain pipes had a significant yield loss of 39% (p < 0.001)

relative to cranberries growing over properly functioning drain pipes. Indeed, the yield was 21951

kg ha-1 in the poorly drained section and 36135 kg ha-1 in the well drained section. Although it was

not measured, the yield reduction in the poorly drained section most likely persisted in the

subsequent years, because of plant death.

Analyses of the soil solution did not detect Mn, but resulted in Fe2+ concentration of more than 5.0

ppm, i.e. the maximum value detectable by the color disk. According to Ford (1982), Fe2+ levels

above 2.5 ppm are problematic for drainage systems and often present severe ochre problems. A

concentration of 24% of organic matter (dry wt.) was found in the swollen masses, much higher

than the ~1% typically found in sandy beds. Similar concentrations (~20%) were found in ochre

deposits in Scotland (Wheatley, 1988). Although the sulfur concentration was not measured, the

color, the smell, the presence of organic matter and iron, indicated the swollen masses to be iron

ochre mixed with sulfur slime (Ford, 1993).

As Fe2+ can complex with many organic compounds (Wheatley, 1988), the organic fertilizers added

to the soil surface may have migrated inside the drain pipes, then becoming potential sources of

energy for ochre formation. The Fe2+ in solution in the drainage water is further oxidized by the

action of heterotrophic bacteria using the soluble Fe-organic matter complex as an energy source or

by filamentous bacteria (Wheatley, 1988). These reactions result in the formation of gelatinous iron

ochre deposition adhering to the drain pipe walls and consisting of bacterial filaments that have

adsorbed colloidal Fe3+, ions such as silica, silt and quartz, as well as other amorphous material

(Wheatley, 1988).

4.3. Case study #2

In the second case study, a drainage problem was suspected in half of a bed (454 m long and 45 m

wide) cropped in conventional production and planted with the Stevens variety in 2003. By

investigating the temporal variation of tensiometers values (model HXM80; Hortau, Lévis, Québec,

Canada) after two rainfall events during blooming, we observed that SWP remained above the

problematic threshold (> -3.0 kPa) for 18 h longer (52 vs 34) in one half of the bed (Figure 4.3a).

By inspecting the drainage system, it was found that the corresponding drainage outlet was closer to

the ground than the drain pipes, thereby decreasing the hydraulic head and slowing drainage. This

problem was corrected by moving the drainage outlet below the lateral drain depth. The drainage

time was then similar between both parts of the bed (Figure 4.3b). The yield was estimated by

56

harvesting samples (n=204; 929 cm2/sample) in each of the two sections in 2011; this sampling was

repeated in 2012 for evaluating the impact of the correction. The yield difference between the two

sections was analysed using the GLM (generalized linear model) function of R (R Foundation for

Statistical Computing, Vienna, Austria).

a b

Figure 4.3. Temporal variations of soil water potential values after the end of rainfall (time=0) until it return to the target of -3 kPa in both section (West vs East) of a cranberry bed. In a) rainfall was 29 mm; the depth of the drainage outlet was problematic at the West extremity of the bed and in b) rainfall was 26 mm; the drainage outlet problem was corrected.

In 2011, a significant yield reduction of 25% (p < 0.001) was measured in the section with slower

drainage (32884 kg ha-1) compared to the faster drainage section (43624 kg ha-1). After correcting

the problem, the yield difference between both parts of the bed became non-significant the next year

(p = 0.12; 44003 kg ha-1 vs 47167 kg ha-1).

4.4. Practical implications

Even if the two drainage problems presented in this paper led to yield losses of 25 and 39%, they

were diagnosed in good yielding beds. In the case of low yielding beds, the drainage efficiency

should be investigated to verify if drainage problems could be an explanation of the low yields.

Some actions could be taken for limiting the detrimental effect of clogged drains on cranberry yield.

The use of tensiometers could have prevented the problem early in the growing season by

monitoring SWP. Including access chimneys to the drain pipe network is inexpensive and may be

very useful when clogging problems are suspected. A pushrod inspection camera can be used to

look inside the drain and evaluate the clogging problem. Because cranberries are cultivated over

sandy soils and that iron ochre is more susceptible to deposit in drain pipes installed in sandy soils

(Gameda et al., 1983; Ford, 1982), the problem of clogging drains by organic slime is of particular

importance in production of organic cranberries. Washing drain pipes with injection of water can

-3

-2

-1

0

1

-6 0 6 12 18 24 30 36 42 48 54

So

il w

ater

po

ten

tial

(kP

a)

Time (h) since rainfall ended

West

East

-3

-2

-1

0

1

-2 0 2 4 6 8 10

So

il w

ater

po

ten

tial

(kP

a)

Time (h) since rainfall ended

57

temporarily correct the problem but more investigations have to be done to permanently solve this

problem. The voids in the soil are also suspected to be clogged by the organic slime, which could

considerably reduce the soil hydraulic conductivity and warrant further investigations.

Using tensiometers allowed diagnosing the drainage problem related to the drainage outlet and

applying an adequate correction. Because the original design of the drainage system dated from

2003, the yield reduction may have occurred during many years. Since the drainage duration (> 24

h) was sufficiently long to result in hypoxic conditions affecting plant productivity (Pelletier et al.,

2016), even in the faster drainage section of the bed, the drain pipes spacing is probably too wide

for adequate drainage and improvement of the drainage design also warrants further investigation.

4.5. Conclusion

Cranberry is very sensitive to poor drainage conditions. These two cases clearly show that even if

this crop is believed to be tolerant to excess water, it must be grown in beds in which the drainage

system is fully effective to avoid cranberry yield losses. In this study, yield losses of 39% were

measured when drain pipes were clogged, and of 25% due to a faulty design/construction of the

drainage outlet. These two cases show that the design and maintenance of a properly functioning

drainage system is of prime importance for maximizing yield and, therefore, warrant a close follow-

up with appropriate equipment and access structure.

4.6. Acknowledgements

The authors of this paper acknowledge the financial contribution of the Natural Sciences and

Engineering Research Council of Canada, Fonds de Recherche Nature et Technologies du Québec,

Nature Canneberge, Canneberges Bieler, Transport Gaston Nadeau, Hortau and the Scientific

Research and Experimental Development Tax Incentive Program of the Canada Revenue Agency

and Revenu Québec.

58

4.7. References

Baumann, D. L., Workmaster, B. A., Kosola, K. R. 2005. ‘Ben Lear’ and ‘Stevens’ cranberry root and shoot growth response to soil water potential. HortScience. 40: 795-798.

Ford, H.W. 1979. Characteristics of slime and ochre in drainage and irrigation systems. Trans. Am. Soc. Ag. Eng. 22: 1093-1096.

Ford, H.W. 1982. Estimating the potential for ochre clogging before installing drains. Trans. Am. Soc. Ag. Eng. 25: 1597-1600.

Ford, H.W. 1993. Iron ochre and related sludge deposits in subsurface drain lines. Reviewed December 2005 by Hamon, D.Z. Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Services, University of Florida.

Gallichand, J., Lagacé, R. 1987. Modeling sediment movement into perforated subsurface drains. Trans. Am. Soc. Ag. Eng. 30: 119-124.

Gameda, S., Jutras, P. J., Broughton, R. S. 1983. Ochre in subsurface drains in a Quebec fine sandy soil. Can. Agric. Eng. 25: 209-213.

Laurent, T. 2015. Réponse de la canneberge (Vaccinium macrocarpon Ait.) à l’aération du sol. Master’s Thesis, Université Laval, Québec, QC, Canada.

Pelletier, V., Pepin, S., Laurent, T., Gallichand, J., Caron, J. 2016. Cranberry gas exchange under short-term hypoxic conditions. HortScience. (Accepted).

Wheatley, R. E. 1988. Ochre deposits and associated bacteria in some field drains in Scotland. J. Soil Sci. 39: 253-264.

59

CHAPITRE 5 Reducing Cranberries Heat Stress and Midday Depression with Evaporative Cooling

Vincent Pelletier1, Steeve Pepin1, Jacques Gallichand1 and Jean Caron1

1Département des Sols et de Génie Agroalimentaire, Université Laval, 2425 rue de l’Agriculture, Université Laval, Québec City, Québec, Canada, G1V 0A6;

60

Résumé. Le système d’irrigation par aspersion peut être utilisé en production de canneberges afin

de refroidir le feuillage et d’éviter le stress thermique lorsqu’une température cible est atteinte.

L’objectif de cette étude était de déterminer : (i) la température critique du feuillage pour démarrer

l’irrigation, (ii) les effets combinés des stress thermiques et hydriques et, (iii) les effets bénéfiques

de l’irrigation de refroidissement sur les paramètres microclimatiques au champ et sur la

physiologie des plantes. L’assimilation du CO2 (An) était maximale lorsque la température se situait

entre 25 et 29 °C, mais, dû en partie à des limitations stomatiques, a diminué de 11% et de 22%

lorsque la température était respectivement de 33 °C et de 37 °C. Une diminution de la disponibilité

de l’eau dans le sol entraînait une diminution d’An. L’irrigation de refroidissement appliquée au

champ a permis d’abaisser la température du feuillage de 5-10 °C et plus le gradient de pression de

vapeur de l’air dans la canopée était élevé, plus l’irrigation était efficace. Un épisode de

refroidissement par jour appliqué sous des conditions contrôlées a permis un gain de carbone de

19% tout en réduisant les effets négatifs du phénomène de dépression de mi-journée. Plus d’un

épisode de refroidissement par jour n’a pas entraîné de gain de carbone supplémentaire. Parmi les

régions productrices de canneberges, l’État du New Jersey est celle où l’irrigation de

refroidissement pourrait être le plus bénéfique pour limiter les pertes de rendements associées au

stress thermique.

61

Abstract. A cultural practice for cooling cranberry plants and avoiding yield losses due to

overheating is to turn on sprinkler irrigation for a few minutes when a critical temperature threshold

is reached. The purpose of this study was to determine: (i) the critical leaf temperature to start

irrigation for evaporative cooling in cranberry production, (ii) the combined effects of heat and

water stress, and (iii) the beneficial effects of evaporative cooling through irrigation on field

microclimate and plant physiology. The optimum temperature range for carbon dioxide (CO2)

assimilation was between 25 and 29 °C, with photosynthesis (An) declining by 11% at 33 °C and by

22% at 37 °C due in part to stomatal limitations. The reduction in An was greater under low soil

moisture conditions. When applying sprinkler irrigation in the field, leaf temperature was reduced

by 5-10 °C and the efficiency of evaporative cooling was greater, with greater vapor pressure deficit

of the air within the crop canopy before the irrigation. Under controlled environmental conditions,

one cooling event resulted in a carbon gain of 19% relative to untreated plants and was able to

reduce midday depression. Additional cooling events during the day had no significant effect on

carbon gain. Among the main cranberry-growing regions, New Jersey is an area where sprinkler

irrigation for evaporative cooling could be beneficial for preventing yield limitations due to heat

stress.

62

5.1. Introduction

Higher mean air temperatures and increased climate variability, such as more frequent heat waves,

are anticipated for the current century over several regions of the globe (IPCC, 2013). As a

consequence, worldwide agricultural production is predicted to be negatively affected by climate

change with great risks for future global food security. Heat waves can be harmful to plant

development, even in northern latitudes. For instance, in spring 2013, air temperature reached 27 °C

(which is typically 3-5 °C higher in the crop canopy) for three consecutive days (4-7 May) in

Québec, Canada. These temperatures interfered with dormancy and deacclimation in cranberry

(Vaccinium macrocarpon Ait.). Such temperatures were unusual for that time of the year, being ~10

°C higher than the average daily maximum temperature of 16.5 °C. Growers in the Québec region

later reported that there were large sections of the field with dead plants, resulting in yield

reductions of 90-100% over these areas. Because these underperforming sections also corresponded

to the deepest depth of the water table, yield losses were due to a combination of heat and water

stress (Pelletier et al., 2015). The same heat wave also affected forest trees, as evidenced by a

significant decrease in photosynthesis and number of leaves on maple trees (Acer saccharum

Marsh) in Ontario (Canada) (Filewood and Thomas, 2014). Hence, plants face a dilemma when

concurrently exposed to heat stress and water stress: while stomatal closure helps prevent water loss

under drier conditions, it inevitably leads to a lower cooling efficiency of foliage by transpiration

(Mittler, 2006).

For most angiosperm species, plant physiological activity is maximized when air temperature is

between 20 and 30 °C, though the relationship between physiological processes and temperature is

species specific (Teskey et al., 2014). In general, one of the first plant responses to heat stress is a

decline in gas exchange due to stomatal and non-stomatal limitations (Wahid et al., 2007). Little

information is available on the relationship between gas exchange of cranberry fruiting uprights and

temperature. However, there is evidence from photosynthetic light and temperature response curves

performed on young cranberry runners that maximum leaf photosynthesis is reached at a leaf

temperature (TL) of 30 °C (Kumudini, 2004). Because fewer carbohydrates are typically assimilated

under elevated temperatures, morphological responses such as flower sterilization, lower fruit set,

and smaller fruits can lead to a reduction in cranberry yield (Bahuguna et al., 2014, Pagadala et al.,

2000).

While overhead irrigation has traditionally been used in cranberry production to meet plant water

requirements and avoid water stress, recent work has demonstrated that maintaining the water table

63

at an optimal depth (~60 cm) during the growing season results in higher yields while saving water

and pumping energy (Pelletier et al., 2015; Gumiere et al. 2014; Caron et al., 2016). There are

concerns, however, that these new water management practices could increase the risks associated

with heat stress in the future. Indeed, exclusively managing water table depth leads to drier canopy

conditions than sprinkler irrigation, and thus can increase the vapor pressure deficit near the foliage

(VPDF) and the risk of heat stress because of lower relative humidity (RHF) and higher temperatures

(TF) in the canopy. Consequently, plants may be overheating under conditions of high evaporative

demand as they gradually close their stomata to prevent water loss. A cultural practice to cool the

the plants and avoid overheating is to turn on sprinkler irrigation for a few minutes when a critical

temperature threshold is reached. This technique has been successfully applied in field crops (Liu

and Kang, 2006) and fruit production, such as apples (Parchomchuk and Meheriuk, 1996) and pears

(Dussi et al., 1997). Although some cranberry growers are known to use sprinkler irrigation for

evaporative cooling on very hot days, the potential benefits of this technique and the range of soil

water tensions for its applicability have not been thoroughly investigated in cranberry. In addition,

the optimal temperature threshold to initiate irrigation remains unknown.

We hypothesize that when air temperature has reached a critical threshold, cooling cranberry vines

to an optimal leaf temperature with sprinkler irrigation will result in higher plant photosynthetic

activity. Two growth chamber experiments and one field experiment were conducted to complete

the following objectives: 1) to determine, for different soil water availability conditions, the critical

plant temperature threshold at which the physiological activity of cranberry vines is negatively

affected; 2) to investigate the effects of evaporative cooling irrigation on measured environmental

parameters in field conditions; and 3) to evaluate the efficiency of cooling as a mitigation measure

for heat stress under different soil water availability conditions..

5.2. Materials and Methods

5.2.1. Determination of the critical temperature threshold

Experiments were conducted in an 18 m3 walk-in plant growth chamber (BDW80, Conviron,

Winnipeg, Canada) located at the Université Laval in Québec City, Canada (lat. 46°46'N, long.

71°16'W). Mature ‘Stevens’ plants were collected from a commercial cranberry production field

(2% very fine sand; 37% fine sand; 49% medium sand; 12% coarse sand) as a 0.06 m2 mat of vines

and grown in 27-litre containers filled with sand from the same field. Particular attention was paid

to avoid cutting roots and shoots when removing the mat from the field soil. Plants were

64

overwintered in the dark at 4 °C and 80% RH for 6900 hours, satisfying the minimum

recommended chilling time of 2500 hours (Eady and Eaton, 1972). To break dormancy on days 1 to

7, temperature was set at 15 °C from 13:00 to 18:00 h and at 6 °C from 01:00 to 05:00 h with

temperature changes at 1 °C h-1 increment between those periods. Relative humidity followed a time

course similar to temperature, with values of 50% during the day and 80% during the night.

Day/nighttime temperature was set at 21 °C/11 °C from Day 8 to 14 and at 25 °C/16 °C from Day

15 until the end of the experiment. Metal halide high-intensity discharge lamps (n=33, 400 W) were

set to reach a photosynthetic photon flux density (PPFD) of ~600 µmol m-2 s-1 at plant level,

corresponding to light-saturated conditions for cranberry (Kumudini, 2004). Each 27-litre container

was seated in a 76-litre container. Water was added in the large container and holes were drilled in

the bottom of the small container to ensure water entering into the soil by upward flux. A Mariotte

bottle was connected to the large container to replace the water lost by evapotranspiration and to

ensure constant soil water tension (Soppe and Ayars, 2003). Two containers were maintained at a

soil water tension of 3.6 kPa and two at 6.0 kPa.

Net photosynthesis (An), stomatal conductance to water vapor (gs) and transpiration (Tr) were

measured at leaf temperatures (TL) ranging from 21 °C to 37 °C with 4 °C increments. Starting

initially with 21 °C, gas exchange variables were recorded at each TL ~20 min after they had

reached steady state conditions. Measurements were performed at the hook stage (between Day 32

and 37) using two cross-calibrated portable photosynthesis systems (LI-6400XT, Li-Cor, Lincoln,

NE, USA) equipped with a 6-cm2 chamber (6400-02B with a red/blue LED light source, Li-Cor).

On the same fruiting upright, current-year foliage (new leaves) were measured with the first LI-

6400XT, whereas leaves from the two previous years (old leaves) were simultaneously measured

with the second LI-6400XT. The CO2 concentration in both chambers was set at 400 µmol mol-1

with an air flow rate of 400 µmol s-1 and PPFD of 1000 µmol m-2 s-1. Further, VPDL was increased

linearly from 0.8 kPa at 21 °C to 4.7 kPa at 37 °C. A leaf thermocouple was carefully positioned to

measure air rather than leaf temperature and the energy balance method was used for estimating TL

and calculating related gas exchange parameters (see Li-Cor LI-6400 manual for more details).

Measurements were repeated on eight fruiting uprights: four from the containers maintained under

optimal soil water tension (3.6 kPa) and four from the containers subjected to drier soil conditions

(6.0 kPa). Those soil water tension values were determined from the wetting part of the soil water

retention curve, as established in a previous experiment (Pelletier et al., 2015). Leaves were

removed after each measurement and digitalized with a flatbed scanner to determine leaf area using

ImageJ software (W.S. Rasband, U. S. National Institutes of Health, Bethesda, MD, USA). All

65

statistical tests were performed using PROC MIXED in SAS 9.3 and means were compared using

Tukey test at the p = 0.05 significance level (SAS Institute, Cary, NC, USA).

5.2.2. Effect of environmental variables and sprinkler irrigation on cooling efficiency in field conditions

Trials were conducted in 2013 and 2014 on a site located in the Centre-du-Québec region (46°16’N;

71°57’W) in Québec (Canada). Data were collected from six adjacent ‘Stevens’ cranberry beds of

2.1 ha in size (see Pelletier et al., 2015) for more details on water management of these beds).

Irrigation systems were already installed and used for protecting crops from frost injury with

sprinkler spacings of 18 m and irrigation line spacing of 15 m. The recommended operation

pressure at the sprinkler nozzle is 350 kPa for flow rates of 20 LPM at the nozzle and a uniform

water distribution in the bed (sprinkler model VYR-35; Vyrsa, Burgos, Spain). A diesel engine

pump installed in a water supply and automated by a field control unit (CTR, Hortau, Lévis,

Québec, Canada) was used to initiate sprinkler irrigation when the critical temperature threshold

was reached.

Six adjacent beds were used and each bed (2.1 ha) was equipped with three valves for controlling

irrigation (Figure 5.1). One third (0.7 ha; divided equally along the length of the bed) of each bed

was used as a control plot where the first or third valve remained closed during irrigation

treatments. The location of control and treated plots were alternated in each pair of adjacent beds.

The middle part of each bed was cooled, but kept as a buffer zone between the two treatments.

Therefore, both treatments were applied in a same bed. The cooling irrigation treatment was applied

by the opened valves when TF reached 33 °C. This threshold was chosen based on the results of the

first experiment (see Section 5.2.1). Each irrigation event lasted 20 minutes, when the critical

temperature threshold was reached and corresponded to a depth of 1.5 mm of water applied via

irrigation. Vapor pressure deficit in the canopy foliage (VPDF) was calculated from values

monitored by combined TF and RHF sensors (THM, Hortau). It was established in a previous

experiment that foliage temperature (TF) did not differ significantly from air temperature measured

in the crop canopy using THM sensors (data not shown). A complete weather station (Hortau,

Lévis, Canada) was installed beside the beds at a 2-m height for monitoring air temperature (TA,2-m),

air relative humidity (RHA,2-m), wind speed, and solar radiation flux density. Regression models

were used for analyzing the reduction in foliage temperature after a cooling event as a function of

environmental conditions before sprinkling.

66

Figure 5.1. Layout of the six cranberry beds used in the experiment to identify the effects of environmental variables and sprinkler irrigation on cooling efficiency in field conditions. Each bed (2.1 ha; 457 m long and 46 m wide) was equally divided into three zones of 0.7 ha. Dark gray zones were irrigated for 20 minutes when the foliage temperature reached 33°C. White zones were unirrigated control plots. Light gray zones were irrigated but kept as a buffer zone between the two treatments.

5.2.3. Gas exchange responses to cooling treatments

Cranberry plants were grown in the same conditions as those described in Section 5.2.1. A total

dose of 40 kg ha-1 N, 60 kg ha-1 P, and 125 kg ha-1 K was divided into three applications at 10, 50

and 100% of flowering. Fertilizers were mixed with 250 ml of water and applied manually to each

0.06 m2 mat with a watering can. Flowers were hand-pollinated daily with a small paintbrush

between Day 44 and 65. Treatments included three levels of cooling with three levels of soil water

tension. A control treatment (C0) where no cooling was applied was compared to one cooling

episode treatment (C1) and three cooling episodes treatment (C3). One 0.06 m2 mat was maintained

at a soil water tension of 4.0 kPa (T4) corresponding to well-watered conditions, one at 7.5 kPa (T7)

for inducing a mild water stress, and one at 15 kPa (T15) for more severe water stress conditions.

For C3, only T4 and T7 were tested. Each of the eight treatments was replicated randomly between

Day 67 to 87 on three fruiting uprights (n=24, i.e., one new upright per mat per replicate) that had

1-3 berries of approximately 0.5 g each.

Each replication included a first day of measurements (D0) with no heat stress and no cooling

treatments for comparison with the next day of measurements (D1) where the treatments were

applied. Three portable gas exchange systems (LI-6400 and LI-6400XT, Li-Cor) were used in the

same mat each day for recording of An between 08:00-19:00 h at 3-min intervals in each treatment.

A custom-built, cylindrical chamber made of clear polycarbonate (5.4 cm ID x 7.5 cm long) was

installed on each LI-6400 system to measure gas exchange of one fruiting upright (which included

current-year and older foliage, as well as berries) per treatment. Leaf temperature (TL) was initially

set at 21 °C on D0 (by controlling chamber air temperature) and gradually increased to reach 27 °C

at 11:00 h (Figure 5.2). Leaf temperature (TL) was kept constant until 16:00 h and then gradually

lowered to 21 °C (at a rate of 0.5 °C h-1). The PPFD incident at the top of each upright on D0 and

D1 followed a time course similar to TL, with a minimum value of 200 µmol m-2 s-1 at 8:00 h and a

67

maximum value of 1200 µmol m-2 s-1 from 11:00 h to 16:00 h. Leaf chamber illumination was

provided by a red-blue (10% blue) light-emitting diode (LED) panel (TI SmartLamp, LED

Innovation Design, Terrebonne, Québec, Canada). For all treatments (C0, C1 and C3) on D1, TL

was gradually increased from 21 °C at 08:00 h to 33 °C at 11:00 h and gradually decreased from 33

°C at 16:30 h to 21 °C at 19:00 h (Figure 5.2). While TL was kept constant at 33 °C for C0, it was

lowered to 27 °C in 20 min for treatment C1 starting at 11:30 h and gradually increased to 33 °C

over the next 5 h. These changes in TL were repeated three times for C3. A dew point generator (LI-

610, Li-Cor) was used to control chamber RH and closely match the VPD conditions observed

during cooling irrigation in the field (see Section 5.3.2). The CO2 assimilated between 11:30-16:30

h on D0 and D1 was compared to determine the effect of the different treatments.

Figure 5.2. Time course of cranberry leaf temperature (TL) during two days of gas exchange measurements (D0 and D1) for three cooling treatments (C0: control, C1: one event, and C3: three events). Experiments were performed under controlled environmental conditions in a growth cabinet and changes in leaf temperature were induced by heating/cooling air in the chamber of the LI-6400 portable gas exchange system.

Treatment effects were separated using Dunnett’s test for time-integrated values of An on D0, D1

and the difference in total CO2 gain between D1 and D0. To eliminate the large difference (typically

1-3 µmol m-2 s-1) in gas exchange values among stems, the data were standardized with respect to

the maximum value of each stem. The treatment with no cooling was used as the cooling control

and the treatment at 4.0 kPa was used as the tension control. Linear and quadratic contrasts were

carried out separately for cooling and tension treatments to investigate the behavior of the

relationship between An and water stress, heat stress and combined water and heat stresses. All

statistical tests were performed using PROC MIXED in SAS 9.3 and means were compared using

Dunnett test at the p = 0.05 significance level (SAS Institute, Cary, NC, USA).

19

21

23

25

27

29

31

33

35

07:0

008

:00

09:0

010

:00

11:0

012

:00

13:0

014

:00

15:0

016

:00

17:0

018

:00

19:0

020

:00

TL

(°C

)

Time of the day

C0C1C3

D0 (C0, C1, C3)

D1:

68

5.3. Results

5.3.1. Determination of the critical temperature threshold

Maximum An was reached on average at a temperature range of 25-29 °C while at 33 °C, An was

significantly lower (by ~11%) and continued to decline at 37 °C with a significant reduction of 22%

(Figure 5.3a). Photosynthesis (An) was approximately two times higher in old leaves than in new

leaves (Figure 5.3d) and the decline in An with increasing TL was more drastic for uprights exposed

to a mild water stress (i.e., 6.0 kPa). As An declined at high leaf temperature, there was a

concomitant reduction in gs resulting in a decrease of mean intercellular CO2 concentration (Ci)

from 334 µmol CO2 mol-1 at 21 °C to 240 µmol CO2 mol-1 at 37 °C (data not shown). Moreover, gs

declined linearly with increasing temperature for both leaf types and soil water conditions (Figure

5.3b). Surprisingly, mild water stress conditions had an impact on gs of old leaves, with absolute gs

values being 42% lower at 6.0 kPa than at 3.6 kPa (Figure 5.3d). The effect of a slight water

limitation was also apparent on transpiration, which started to decline significantly at 37 °C in old

leaves under water stress (Figure 5.3c). Based on these results, a temperature threshold of 33 °C

was established for cranberry, suggesting that sprinkler irrigation should be turned on when TL

reaches 33 °C to avoid heat stress and maximize carbon assimilation.

5.3.2. Effect of environmental variables and sprinkler irrigation on cooling efficiency in field conditions

Effects of sprinkler irrigation were examined during 10 field events (4 in July 2013 and 6 in June-

July 2014). On average, irrigation was started when TF reached 33 ± 1 °C and in general, TA,2-m was

only 28 ± 2 °C when treatments were initiated. After 20 min of irrigation, TF declined (ΔTF) by 6.6

± 1.5 °C and RHF increased from 53 ± 11% to 85 ± 5%. This corresponded to a VPDF of 2.4 ± 0.6

kPa before irrigation and 0.6 ± 0.2 kPa after irrigation. There was a significant linear relation

between the cooling efficiency of irrigation events and ΔTF (Figure 5.4). Overall, mean duration

efficiency (i.e., time required for TF in irrigated plots to return to values similar to those in non-

irrigated plots) was 168 ± 33 minutes (Figure 5.4). This 20% variability in cooling efficiency was

attributable to the broad range of environmental conditions prior to irrigation (Figure 5.5). Vapor

pressure deficit in the canopy foliage (VPDF) was the most significant variable for cooling

efficiency (Figure 5.5a), followed by RHF (Figure 5.5b), TA,2-m (Figure 5.5c) and wind speed

(Figure 5.5d). In contrast, solar radiation (Figure 5.5e) and RHA,2-m (Figure 5.5f) were not

significant (p > 0.05).

69

a

b

c

d

Leaves - Soil water tension An (µmol CO2 m-2 s-1) gs (mol H2O m-2 s-1) Tr (mmol H2O m-2 s-1)

New leaves - 6.0 kPa 3.93 0.12 1.48

Old leaves - 6.0 kPa 6.22 0.14 3.24

New leaves - 3.6 kPa 3.42 0.13 1.93

Old leaves - 3.6 kPa 7.90 0.24 4.37

Figure 5.3. Standardized (a) photosynthesis (An), (b) stomatal conductance (gs), and (c) transpiration (Tr) in relation to leaf temperature (TL) and soil water tension. Gas exchange values of each stem were standardized with respect to their maximum value. According to Tukey’s test, mean ± S.E. values with the same letter are not significantly different (p < 0.05) from one another for each combination (n=4) of new (N) and old (O) leaves at each soil water tension (3.6 vs 6.0 kPa). White bars indicate the overall mean values of leaf age and soil tension. Values corresponding to the maximum for each combination of leaves and soil water tension are presented in (d). On each fruiting upright, there were 10 ± 2 new leaves with an average total leaf area of 3.0 ± 1.4 cm2 and 15 ± 4 old leaves with a mean total leaf area of 2.9 ± 0.8 cm2.

50%

60%

70%

80%

90%

100%

An

aa a

b

c

ba

a a

c

aa a

b

c

c aba a

bc ba a

b

c

20%

40%

60%

80%

100%

g s

aa

b

c

c

a ab b

c

d

ab

c

dd

ab

c

c

d

a

c

b

d

e

20%

40%

60%

80%

100%

21 25 29 33 37

Tr

TL (°C)

b ab

a aab

21 25 29 33 37

TL (°C)

d

c

b

ab

21 25 29 33 37

TL (°C)

c

bab ab a

21 25 29 33 37

TL (°C)

d

c

b

a a

21 25 29 33 37

TL (°C)

c

b

aa a

N - 6.0 kPa O - 6.0 kPa N - 3.6 kPa O - 3.6 kPa Average

70

Figure 5.4. Efficiency of evaporative cooling in relation to the difference in temperature of cranberry foliage (ΔTF) immediately before and after the sprinkler irrigation. Data are from field experiments where irrigation was initiated when TF reached 33 °C.

Figure 5.5. Difference in temperature of cranberry foliage (ΔTF) due to evaporative cooling as a function of environmental conditions just before irrigation. (a) Vapor pressure deficit in the canopy foliage (VPDF), (b) relative humidity in the canopy foliage (RHF), (c) air temperature at the weather station (TA,2-

m), (d) wind speed, (e) solar radiation (Rad), and (f) relative humidity at the weather station (RHA,2-m).

A representative experimental irrigation treatment event is presented in Figure 5.6. There was an

increase in RHF from 39 to 91% and a decrease in TF from 34.1 to 26.7 °C after irrigation, resulting

in a decline in VPDF from 3.2 kPa just before irrigating (12:30 h) to 0.5 kPa right after irrigating.

Wind speed was 5.5 km h-1 and solar radiation was 792 W m-2 at the time of irrigation, whereas TA,2-

m was 7.0 °C lower than TF just before irrigation. The cooling irrigation was effective until 16:00 h

at which time the temperature in the irrigated foliage and non-irrigated foliage was approximately

the same.

0123456

0 2 4 6 8 10 12

Eff

icie

ncy

(h)

ΔTF (°C)

R2 = 0.88p < 0.001

y = 3.09e0.31x

R² = 0.87, p < 0.00102468

1012

1 2 3 4

ΔT

F(°

C)

VPDF (kPa)

a

y = 224.88x-0.90

R² = 0.79, p < 0.00102468

1012

30 40 50 60 70

ΔT

F(°

C)

RHF (%)

b

y = 19 297.42x-2.40

R² = 0.57, p = 0.0102468

1012

24 27 30 33

ΔT

F(°

C)

TA,2-m (°C)

c

y = 15.66x-0.40

R² = 0.48, p = 0.0302468

1012

0 5 10 15 20 25

ΔT

F(°

C)

Wind (km/h)

d

y = 2.06e0.00x

R² = 0.34, p = 0.0702468

1012

400 500 600 700 800 900

ΔT

F(°

C)

Rad (W m-2)

e

y = 11.77e-0.01x

R² = 0.34, p = 0.0802468

1012

20 30 40 50 60 70

ΔT

F(°

C)

RHA,2-m (%)

f

71

Figure 5.6. (a) Temperature and (b) relative humidity in the canopy foliage of non-irrigated and irrigation treatments and at the weather station between 08:00-20:00 h on June 27th 2014.

5.3.3. Gas exchange responses to cooling treatments

Averaged values of An (between 11:30-16:30 h) on D0 (An-D0) and D1 (An-D1), as well as the

difference in assimilated carbon between D1 and D0 (ΔAn) are given in Table 5.1 for each cooling

and soil tension treatment. The effect of C1 on ΔAn (+12%) was significantly greater than C0 (-7%)

when comparing measurement on both days. An average C gain of 19% is then expected with a

single cooling irrigation treatment. However, the relationship between the number of cooling

episodes and ΔAn was quadratic and more than one cooling episode had no significant effect on the

carbon gain of fruiting uprights.

Table 5.1. Photosynthesis of cranberry fruiting uprights (n=6 to 9 per treatment) averaged over a 5 h period (11:30-16:30) on Day 0 (An-D0), Day 1 (An-D1), and the difference between Day 1 and Day 0 (ΔAn) for each cooling treatment (C0: control, C1: one event, and C3: three events) and soil water tension (SWT) treatment (T4: 4.0 kPa, T7: 7.5 kPa, and T15: 15.0 kPa). Cooling events were initiated when temperature in the foliage reached 33 °C. In the Dunnett test, treatment C0 was used as a control for testing the cooling effect and treatment T4 was used as a control for testing the SWT effect. The fruiting uprights had on average 39 ± 5 leaves and a total leaf area of 7.9 ± 1.4 cm2.

Treatment nAn-D0 An-D1(µmol CO2 m-2 s-1)

ΔAn (Day1 vs Day0)

Dunnett test (p<0.05)

Cooling treatment

C0 9 5.4 5.1 -7% -

C1 9 5.8 6.5 12% *

C3 6 5.7 6.0 2% N.S.z

Linear Contrast (p<0.05) N.S. N.S. N.S. Quadratic Contrast (p<0.05) N.S. N.S. *

SWT (kPa)

T4 9 6.5 7.1 9% -

T7 9 5.4 5.5 0% N.S.

T15 6 4.7 4.6 -3% N.S.

Linear Contrast (p<0.05) N.S. * N.S. Quadratic Contrat (p<0.05) N.S. N.S. N.S.

z: Non-significant

72

Mean An-D0 values were similar across all cooling treatments, indicating that the photosynthetic

potential of all stems was equal before treatment application (Table 5.1). Photosynthesis (An) was

more affected when water and heat stresses were combined than when only water stress was

considered. Indeed, there was a significant linear effect for An-D1, but none for An-D0. Photosynthesis

on Day-1 (An-D1) was 22.5% lower under mild water stress (7.5 kPa) and 35.2% lower for a more

severe water stress (15.0 kPa) when compared with well-watered conditions (4.0 kPa). These results

are consistent with those of Section 5.3.1 where An of old leaves was 24.6% and 36.3% lower under

mild water stress (6.0 kPa) than in the control treatment (3.6 kPa) at 33 °C and 37 °C, respectively.

A decline in An was observed at ~10:00-12:00 h in approximately half of the stems and

corresponded to a phenomenon called midday depression. Between 12:00-17:00 h, An recovered by

slightly increasing in the cooling treatment (Figure 5.7a). For the remaining half of the stems, An

remained unchanged between 10:00-17:00 h (Figure 5.7b). Under conditions of no heat stress (i.e.,

D0), An at 15:00 h was 9.9% lower than the maximum daily value and there was no difference

among the treatments (Table 5.2). When a heat stress was applied on D1, treatments C1 and C3

significantly reduced the midday depression effects in comparison with C0. Indeed, An was

approximately 20% lower at 15:00 h than the maximum daily value for C0, 3.6% lower for C1 and

was 0.3% higher for C3.

Figure 5.7. (a) Midday depression of photosynthesis (An) observed at ~11:00 h on Day 1 when cranberry leaf temperature (TL) in the LI-6400 chamber was increased from 21 °C to 33 °C whereas on Day 0, TL was kept constant at 27°C from 11:00 to 17:00 h. The arrow indicates one cooling episode when TL was decreased to 27 °C, thereby simulating the effect of evaporative cooling by sprinkler irrigation. In this case, soil water tension was 7.5 kPa. (b) Absence of a midday depression. Here, there was no cooling episode and soil water tension was 4.0 kPa.

18

21

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73

Table 5.2. Effect of cooling treatments (C0: control, C1: one event, and C3: three events) on photosynthetic midday depression (An-loss) of cranberry fruiting uprights, calculated as the difference between the maximum rate of photosynthesis in the morning and that measured at 15:00 h (averaged over 15 minutes). Soil water tension treatments were pooled and treatment C0 was used as a control in the Dunnett test. Cooling events were initiated when the temperature in the foliage reached 33 °C.

D0 D1

Cooling An-loss

(µmol CO2 m-2 s-1)Dunnett test

(p<0.05) An-loss

(µmol CO2 m-2 s-1)Dunnett test

(p<0.05)

C0 -0.84 - -1.13 -

C1 -0.48 N.S.z -0.22 *

C3 -0.36 N.S. 0.04 *

z: Non-significant

5.4. Discussion

5.4.1. Determination of the critical temperature threshold

As expected, net photosynthesis (An) of fruiting uprights varied with leaf temperature, reaching a

maximum value between 25-29 °C, followed by a significant decline at higher temperatures (~11%

and 22% reduction at 33 °C and 37 °C, respectively; Figure 5.3a). On that basis, 33 °C was

established as the critical leaf temperature for cranberry CO2 assimilation. This is consistent with

results from a study that examined 83 species of C3 plants and showed that the optimal temperature

for photosynthesis ranged from 25 °C to 30 °C (Yamori et al., 2013). In contrast, Kumudini (2004)

reported slightly lower values (~2–3%) of photosynthesis in cranberry leaves exposed to 35 °C

compared with those at 30 °C. Interestingly, cranberry seems to be much more tolerant to high

temperature than highbush blueberry, a well-studied Vaccinium species which has a temperature

optimum lower than 20 °C (Moon et al., 1987). For instance, CO2 assimilation of highbush

blueberry has been found to decrease by 22% to 51% (depending on the cultivars) when increasing

leaf temperature from 20 to 30 °C (Hancock et al., 1992). In grapevines, An of the cultivar

‘Semillon’ declined by 35% after the first day of four consecutive days of exposure to a day/night

temperature regime of 40 °C/25 °C and the final yield was 49% lower than in the control treatment

where vines were exposed to 25 °C/15 °C (Greer and Weston, 2010). Because plant tolerance is

also influenced by exposure to previous conditions, acclimation may play an important role in plant

responses to high temperatures.

Because of the cumulative effect of repeated reductions in An associated with heat stress, extreme

high temperature events during the growing season could also lead to significant yield loss in

cranberry production. We examined the climatic data over the last 15 years (1990-2014) for seven

74

of the most productive cranberry-growing regions in North America. Based on the number of days

where daily maximum air temperature (TA-max) reached at least 28 °C (which corresponds to a TF of

~33 °C, a temperature inducing heat stress in cranberry; see Section 5.3.2), our analysis suggests

that cooling irrigation could be particularly beneficial in New Jersey, a region having on average 95

days per year with TA-max > 28 °C (Table 5.3). DeMoranville et al. (1996) and Degaetano and

Shulman (1987) have noted previously that high temperature was an important limiting factor for

cranberry production in New Jersey. Cooling irrigation could also be important in Wisconsin,

Massachusetts and Québec, where TA-max > 28 °C was observed on 37, 23, and 14 days per year,

respectively (Table 5.3). However, the benefits of cooling irrigation would not be substantial in

Oregon, Washington and British Columbia where TA-max > 28 °C generally occurred in only 1, 3,

and 8 days per year over the last 15 years.

Table 5.3. Number of days on a yearly basis (1990-2014) where the daily maximum air temperature (TA-

max) reached values from 25 to 37°C for the seven most productive cranberry-growing regions in North America. Temperature data were recorded at weather stations located near the center of each production region.

Region (Country) City Number of days where TA-max (°C) was reached

25 26 27 28 29 30 31 32 33 34 35 36 37

NJ (USA) Hammonton 134 127 110 95 77 56 48 31 18 10 5 3 1

WI (USA) Marshfield 78 70 53 37 24 13 10 5 2 1 0 0 0

MA (USA) East Wareham 60 53 39 23 15 9 7 4 2 1 0 0 0

QC (CA) Laurierville 40 29 20 14 8 3 2 1 0 0 0 0 0

BC (CA) Richmond 32 20 13 8 5 3 1 1 0 0 0 0 0

WA (USA) Grayland 7 6 4 3 2 1 1 1 0 0 0 0 0

OR (USA) Bandon 3 2 1 1 1 0 0 0 0 0 0 0 0

The decrease in An with increasing TL occurred concomitantly with a pronounced reduction in gs.

Such stomatal closure, a well-known mechanism that allows plants to reduce water loss and cope

with stress conditions, has been shown to lower photosynthesis by limiting CO2 diffusion and

decreasing Ci. Accordingly, the photosynthetic responses of cranberry uprights to temperature were

partly attributed to stomatal limitations (mean reduction in Ci of ~28% between 21 and 37 °C; data

not shown). In fruiting uprights, gs values were highest (0.24 mol H2O m-2 s-1) in old leaves at 21 °C

under well-watered soil conditions and lowest (0.02 mol H2O m-2 s-1) in new leaves at 37 °C under

water stress. These values are similar to those measured by Kumudini (2004) on well-watered

cranberry plants (gs = 0.06-0.30 mol H2O m-2 s-1). In contrast, Croft et al. (1993) found an average

gs of only 0.02 mol H2O m-2 s-1 based on 993 leaf measurements (mean gs = 0.046 cm s-1, converted

to molar units using TA=25 °C and atmospheric pressure=101.3 kPa) and an inverse linear

relationship between gs and TL. With soil water tension at 3.6 kPa, leaf transpiration increased from

21°C to 37 °C, but started to decline at 37 °C in old leaves when it was 6.0 kPa (Figure 5.3c).

75

Because transpiration generally increases with VPD and temperature (Zhao et al., 2013), the decline

of transpiration was a good indicator of soil water limitation under high evaporative demand.

Surprisingly, An was approximately two times higher in old leaves than in new leaves (Figure 5.3a).

This is contrary to the results of Hagidimidriou and Roper (1995) who reported that new leaves are

the primary source of carbohydrates for fruit development (see also Roper and Klueh (1996))

because the CO2 assimilation rate was approximately twice as high in current-year as in one-year-

old leaves. While the differences in photosynthesis of old leaves were quite substantial between the

two studies (~3-4 vs ~6-8 µmol CO2 m-2 s-1 here), our gas exchange measurements were performed

on relatively young new leaves (one-month-old) compared with those sampled by Hagidimidriou

and Roper (1995), which might explain the lower photosynthesis rate observed in our study.

5.4.2. Effect of environmental variables and sprinkler irrigation on cooling efficiency in field conditions

Sprinkler irrigation was efficient at reducing TF by 6.6 ± 1.5 °C and increasing RHF from 53 ± 11%

to 85 ± 5%, thereby lowering VPDF from 2.4 ± 0.6 kPa to 0.6 ± 0.2 kPa. Cooling irrigation was

more effective when VPDF was high (Figure 5.5a) and RHF (Figure 5.5b) and TA,2-m (Figure 5.5c)

were low just before irrigation. These results are consistent with the literature. In a study on wheat,

a short episode of cooling irrigation water significantly decreased the canopy temperature by 6.7 to

10.8 °C (Liu and Kang, 2006). Yield was 4.3% higher in the wheat field that was cooled through

sprinkler irrigation than in the control field, while ΔTF after cooling was primarily related to air

temperature (R2 = 0.39), wind speed (R2 = 0.33) and relative humidity (R2 = 0.27). In orchards, ΔTF

declined by 5-7 °C after cooling and low RH increased the relative effect (Lakatos et al., 2012). In

bush beans, RH (R2= 0.63) had the greatest influence on ΔTF, while wind speed was less related (R2

= 0.26) (Hobbs, 1973). Because the effects of cooling is influenced by duration and is significantly

related to ΔTF (Figure 5.7), our results suggest that more than one irrigation event could be useful

for avoiding heat stress on hot and dry days.

5.4.3. Gas exchange responses to cooling treatments

Cooling the vines when the temperature in the canopy had reached 33°C was effective to avoid the

negative effect of heat stress on An (Figure 5.1). However, although additional irrigation events

were successful in maintaining TL under 33 °C (see Figure 5.6), they did not enhance further carbon

assimilation. Given the recent evidence that controlling the water table at an optimal depth (i.e.,

providing sufficient upward water flux to the rhizosphere) is essential for increasing cranberry yield

(Pelletier et al., 2015), such water management practice is even more important under high

76

temperature conditions, because a significant reduction of An was observed when heat and water

stresses were concurrent (Table 5.1). However, because water table control also affects the

development of cranberry roots (Baumann et al., 2005), the determination of an optimal water table

depth that would avoid water stress conditions and simultaneously reduce heat stress or the need for

evaporative cooling in cranberry crops warrants further investigation.

Diurnal patterns of An indicated the presence of a midday depression in some of the uprights that

were sampled (Figure 5.6). This phenomenon was first reported in cranberry fields by

Hagidimitriou and Roper (1995): An peaked 2-3 hours after sunrise and then decreased by 16% in

the afternoon. It was also reported by Kumudini (2004) where photosynthesis reached its daily

maximum apporximately 09:00-10:00 h and dropped by approximately 50% at 13:00 h.

Measurements in these experiments were performed under field conditions on young leaves that

were 2- to 3- month-old, container-grown cuttings of the ‘Stevens’ cultivar and this probably

explained such large reductions in An. Interestingly, one possible explanation provided by

Kumudini (2004) is that midday depression could depend on microclimatic conditions.

In this study, An generally started to decline at approximately 10:30 h when TL had reached 27 °C.

Furthermore, in comparison with maximum An values observed in the morning, An was reduced by

10% when afternoon temperature was 27 °C and VPDL was 1.7 kPa and by 20% at 33 °C and a

VPDL of 3.3 kPa, thus suggesting that heat stress can increase midday depression. However, cooling

treatments were effective in limiting midday depression, because VPDL declined to 0.9 kPa and the

reduction in An was only 2%. Our results are consistent with those obtained for many other crops.

For example, midday depression occurred when a combination of high temperature and low relative

humidity led the VPD to exceed 2-3 kPa in strawberry trees (Arbutus unedo; Raschke and

Resemann, 1986), 2 kPa in maize (Zea mays; Hirasawa and Hsiao, 1999) and 2 kPa in nectarine

trees (Prunus persica var. nectarina; Osorio et al., 2006). Although our experiments were not

designed to study cranberry midday depression, cooling the plants was effective in avoiding this

negative phenomenon.

5.5. Conclusion

Under the controlled environmental conditions of the experiment, cranberry heat stress started when

leaf temperature reached 33 °C. In field conditions, this corresponded to an air temperature of 28 °C

at 2 m height. Cooling the foliage at 33 °C for 20 minutes reduced foliage temperature by 5.0-10.2

°C and was effective for 2-5 hours. Carbon dioxide assimilation of uprights was significantly

77

increased following a cooling treatment in comparison with no cooling treatment. Moreover, the

midday depression phenomenon was mostly avoided after cooling irrigation.

5.6. Acknowledgements

The authors of this paper acknowledge the financial contribution of the Natural Sciences and

Engineering Research Council of Canada, Fonds de Recherche Nature et Technologies du Québec,

Nature Canneberge, Canneberges Bieler, Transport Gaston Nadeau, Hortau and the Scientific

Research and Experimental Development Tax Incentive Program of the Canada Revenue Agency

and Revenu Québec.

78

5.7. References

Bahuguna, R.N., Jagadish, K.S.V., Coast, O. Wassmann, R. 2014. Plant abiotic stress: Temperature extremes. Encyclopedia of Agriculture and Food Systems, Volume 4. pp 330-334.

Baumann, D.L., Workmaster, B.A., Kosola, K.R. 2005. ‘Ben Lear’ and ‘Stevens’ cranberry root and shoot growth response to soil water potential. HortScience. 40: 795-798.

Caron, J., Pepin, S., Bonin, S., 2016. Determination of irrigation set points for cranberries from soil and plant based measurements. Can. J. Soil Sci. 96: 37-50.

Croft, P.J., Shulman, M.D., Avissar, R. 1993. Cranberry stomatal conductivity. HortScience. 28: 1114-1116.

Degaetano, A.T., Shulman, M.D. 1987. A statistical evaluation of the relationship between cranberry yield in New Jersey and meteorological factors. Agric. For. Meteorol. 40: 323-342.

DeMoranville, C.J., Davenport, J.R., Patten, K., Roper, T.R., Strik, B.C., Vorsa, N., Poole, A.P. 1996. Fruit mass development in three cranberry cultivars and five production regions. J. Amer. Soc. Hort. Sci. 121: 680-685.

Dussi, M.C., Sugar, D., Azarenko, A.N., Righetti, T.L. 1997. Effects of cooling by over-tree sprinkler irrigation on fruit color and firmness in ‘Sensation Red Bartlett’ pear. HortTechnology. 7: 55-57.

Eady, F.C., Eaton, G.W. 1972. Effects of chilling during dormancy on development of the terminal bud of the cranberry. Can. J. Plant Sci. 52: 273-279.

Filewod, B., Thomas, S.C. 2014. Impacts of a spring heat wave on canopy processes in a northern hardwood forest. Glob. Change Biol. 20: 360-371.

Gumiere, S. J., Lafond, J. A., Hallema, D. W., Périard, Y., Caron, J., Gallichand, J. 2014. Mapping soil hydraulic conductivity and matric potential for water management of cranberry: Characterisation and spatial interpolation methods. Biosyst. Eng. 128: 29-40.

Greer, D.H., Weston, C. 2010. Heat stress affects flowering, berry growth, sugar accumulation and photosynthesis of Vitis vinifera cv. Semillon grapevines grown in a controlled environment. Func. Plant Biol. 37: 206-214.

Hagidimitriou, M., Roper, T.R. 1995. Seasonal changes in CO2 assimilation of cranberry leaves. Sci. Hort. 64: 283-292.

Hancock, J.F., Haghighi, K., Krebs, S.L., Flore, J.A. 1992. Photosynthetic heat stability in highbush blueberries and the possibility of genetic improvement. HortScience. 27: 1111-1112.

Hirasawa, T., Hsiao, T.C. 1999. Some characteristics of reduced leaf photosynthesis at midday in maize growing in the field. Field Crops Res. 62: 53-62.

Hobbs, E.H. 1973. Cooling with sprinklers. Can. Ag. Eng. 15: 6-8.

IPCC (Intergovernmental Panel on Climate Change). 2013. Climate change 2013: The physical Science basis. Contribution of working group I to the Fifth assessment report of the IPCC. Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S.K., Boschung, J., Nauels, A., Xia, Y., Bex, V.,

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Midgley, P.M. (eds). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Kumudini, S. 2004. Effect of radiation and temperature on cranberry photosynthesis and characterization of the diurnal change in photosynthesis. J. Am. Soc. Hort. Sci. 129: 106-111.

Lakatos, L., Zyromski, A., Biniak-Pierog, M. 2012. Possibility for modification of microclimate in orchards by using evaporative cooling irrigation. J. Water Land Dev. 16: 29-34.

Liu, H.-J., Kang, Y. 2006. Regulating field microclimate using sprinkler misting under hot-dry windy conditions. Biosyst. Eng. 95: 349-358.

Mittler, R. 2006. Abiotic stress, the field environment and stress combination. Trends Plants Sci. 11: 15-19.

Moon, J.W., Hancock, J.F., Draper, A.D., Flore, J.A. 1987. Genotype differences in the effect of temperature on CO2 assimilation and water use efficiency in blueberry. J. Amer. Soc. Hort. Sci. 112 : 170-173.

Osorio, M.L., Breia, E., Rodrigues, A., Osorio, J., Le Roux, X., Daudet, F.A., Ferreira, I., Chaves, M.M. 2006. Limitations to carbon assimilation by mild drought in nectarines trees growing under field conditions. Environ. Exp. Bot. 55: 235-247.

Pagadala, V., Prasad, V., Craufurd, P.Q., Summerfield, R.J., Wheeler, T.R. 2000. Effect of short episodes of heat stress on flower production and fruit-set of groundnut (Arachis hypogaea L.). J. Exp. Bot. 51: 777-784.

Parchomchuk, P., Meheriuk, M. 1996. Orchard cooling with pulsed overtree irrigation to prevent solar injury and improve fruit quality of ‘Jonagold’ apples. HortScience 31: 802-804.

Pelletier, V., Gallichand, J., Gumiere, S., Pepin, S., Caron, J. 2015. Water table control for increasing yield and saving water in cranberry production. Sustainability. 7: 10602-10619.

Raschke, K., Resemann, A. 1986. The midday depression of CO2 assimilation in leaves of Arbutus unedo L.: diurnal changes in photosynthetic capacity related to changes in temperature and humidity. Planta 168: 546-558.

Roper, T.R., Klueh, J.S. 1996. Movement patterns of carbon from source to sink in cranberry. J. Amer. Soc. Hort. Sci. 121: 846-847.

Soppe, R.W.O., Ayars, J.E. 2003. Characterizing ground water use by safflower using weighing lysimeters. Agr. Water Manage. 60: 59-71.

Teskey, R., Wertin, T., Bauweraert, I., Ameye, M., McGuire, M.A., Steppe, K. 2014. Responses of tree species to heat waves and extreme heat events. Plant. Cell Environ. DOI: 10.1111/pce.12417.

Wahid, A., Gelani, S., Ashraf, M., Foolad, M.R. 2007. Heat tolerance in plants: An overview. Environ. Exp. Bot. 61: 199-223.

Yamori, W., Hikosaka, K., Way, D.A. 2013. Temperature response of photosynthesis in C3, C4, and CAM plants: temperature acclimation and temperature adaptation. Photosynth. Res. DOI: 10.1007/s11120-013-9874-6.

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Zhao, J., Hartmann, H., Trumbore, S., Ziegler, W., Zhang, Y. 2013. High temperature causes negative whole-plant carbon balance under mild drought. New Phytol. 200: 300-309.

81

CHAPITRE 6 Proposing Field Guidelines for Cranberry Water Management: Integrating latest discoveries

Vincent Pelletier1, Jean Caron1, Jacques Gallichand1, Steeve Pepin1, William L. Bland2, Casey D. Kennedy3, and Silvio Gumiere1

1Département des Sols et de Génie Agroalimentaire, Université Laval, 2425 rue de l’Agriculture, Université Laval, Québec City, Québec, Canada, G1V 0A6;

2Department of Soil Science, University of Wisconsin-Madison, 1525 Observatory Drive, Madison, WI, 53706-1299, USA;

3U.S. Department of Agriculture, Agricultural Research Service, Pasture Systems and Watershed Management Research Unit, East Wareham, MA, USA;

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Résumé. Le développement des nouvelles technologies de communication sans-fil permet aux

producteurs de canneberges d’effectuer la gestion de l’eau sur la ferme en temps réel par le suivi à

distance des conditions d’humidité du sol et de la température de l’air. Suite à l’apparition de ces

outils, plusieurs travaux de recherche ont été menés ces dernières années afin de raffiner les

paramètres de gestion de l’eau et d’utiliser de nouvelles stratégies innovatrices. L’objectif de cet

article était d’intégrer les plus récents résultats de recherche afin de proposer les lignes directrices

d’une approche plus intégrée de la gestion de l’eau limitant les principaux stress environnementaux.

Contrôler la nappe à une profondeur de 60 cm et démarrer l’irrigation par aspersion lorsque le

potentiel matriciel de l’eau dans le sol atteint -7.5 kPa permet d’éviter le stress hydrique tout en

maximisant les rendements et en réduisant les quantités d’eau nécessaire et l’énergie de pompage.

Puisque la canneberge est intolérante à des conditions hypoxiques dans la rhizosphère, le maintien

d’un système de drainage entièrement fonctionnel et efficace est primordial pour éviter des pertes

de rendements. Démarrer l’irrigation par aspersion pendant 20 minutes permet d’éviter le stress

thermique lorsque la température du feuillage atteint 33 °C. L’utilisation de cette nouvelle approche

intégrée basée sur les plus récents résultats de recherche permettra d’éviter les principaux stress

environnementaux et de maximiser le rendement agronomique de la canneberge.

83

Abstract. New developments in wireless communication technology allow online soil moisture and

air temperature monitoring and real-time irrigation management in cranberry production. Following

the emergence of these new tools, research was conducted in recent years to improve water

management using innovative strategies. The objective of this paper was to integrate these latest

findings and propose guidelines for a more holistic water management approach. Maintaining the

water table at 60 cm depth and triggering overhead irrigation when soil water potential reaches -7.5

kPa avoid hydric stress, maximize yields and minimize the water volume and energy needed by the

irrigation system. Because cranberry is non-tolerant to hypoxic conditions in the rhizosphere,

maintenance of a properly functioning drainage system is of prime importance to prevent yield

losses. Cooling the vines for 20 minutes through overhead irrigation is necessary for avoiding heat

stress and midday depression when foliage temperature reaches 33 °C. Using a holistic approach

based on the most recent findings will maximize cranberry yields by avoiding the main

environmental stresses.

84

6.1. Introduction

Cultivated cranberry (Vaccinium macrocarpon Ait.) is a biennial plant with flower buds giving on

average 2-4 flowers every other year. Depending on cultivar, approximately half of the flowers set

red berries of 1-2 g mass at harvest. The fine and fibrous roots do not have root hairs and can reach

7-15 cm deep (Sandler and DeMoranville, 2008). Native to the Eastern part of North America, most

production is in USA and Canada (FAOSTAT, 2015). However, approximately 82% of the

cranberries are grown in three regions: Wisconsin, Québec, and Massachusetts (Figure 6.1C). In the

last 10 years, the industry has undergone rapid growth with an increase in total production of 338%

in Québec, 65% in Massachusetts, and 37% in Wisconsin, for a global increase of 60%. Both yield

increase per unit area (Figure 6.1A) and expansion of production areas (Figure 6.1B) explain this

situation.

Figure 6.1. Statistics of the cranberry production for the seven major producing area (BC: British Columbia, MA: Massachusetts, NJ: New Jersey, OR: Oregon, QC: Québec, WA: Washington, WI: Wisconsin). a) Yield, b) Harvested area, and c) Volume.

0

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85

Cranberries are usually grown on a bed made of an impermeable layer surrounded by compacted

berms and over which a layer of medium or coarse sand of variable thickness (15 to 60 cm) has

been added prior to planting. A certain number of draintiles are typically installed at the top of the

impermeable layer to provoke drainage or to allow subirrigation or water level control through

pumping or evacuation of water within the draintiles network.

Production increases have resulted in lower prices and processors seeking berries with both high

natural sugar and total anthocyanin (TAcy) to increase value of the fruit (Nolte, 2015). Therefore, to

remain competitive, growers have then to produce higher quality berries at a lower production cost.

Moreover, growers are facing new constraints based on the strengthening of the health (Wilson,

2015) and environmental regulations (DeMoranville et al., 2015; Kennedy et al., 2015). Irrigation

management has appeared as a key issue for controlling this production under new environmental

constraints and this paper brings together the most recent advances in this facet of management.

Sprinkler irrigation was first used in the 1950s to avoid frost damage to the buds (Eck, 1990). In

order to recirculate the water into the farm, a subsurface drainage system, ditches and reservoirs are

needed. Traditionally cranberry cultivation was understood to depend on relatively wet soil

conditions (Eck, 1990) and the general practice involves applying two hours of irrigation every

other day. Recent analyses (Bonin, 2009; Laurent, 2014; Caron et al., 2016) demonstrated

maximum crop yield and photosynthesis occurs at drier conditions from an empirical relationship

between the average soil water potential and cranberry crop yield and photosynthesis (Figure 6.2).

However, many questions remain unanswered regarding the general relationship of Figure 6.2 and

how to maintain the soil matric potential in the right range for optimal plant growth and yield.

Indeed, the general field relationship reported by Caron et al. (2016) is empirical and an additional

understanding of processes related either to the maintenance of adequate aeration conditions (at the

wet end of the range) or to the limit of water stress (at the drier end of the range) is needed to

generate field guidelines to implement proper overhead and sub-irrigation and proper drainage of

this crop. What is the level of oxygen needed to meet plant requirements, at which growth stage and

how fast should the soil drain to achieve these conditions? Can water table control meet such

requirements? If so, will salts build up at the surface? Is high temperature protection still needed?

Does frost control create hypoxic stress? The objective of this paper is first to summarize the latest

findings related to the above raised questions and second to integrate the latest findings to propose

guidelines for holistic irrigation management using available technologies.

86

Figure 6.2. Empirical relationship between soil water conditions and cranberry yields / photosynthesis. From the general relationship, many questions remained unanswered on the optimum maintain of aeration and water flux.

6.2. Water management strategies

6.2.1. Avoiding water stress

The consumption of water by cranberries has been estimated to be 0.8-6.2 mm day-1 and is

approximately 105% (KC) of evapotranspiration of reference (ETO) when calculated with the

Priestley-Taylor equation (Vanderleest and Bland, 2016). Thus soil water depletion, upward flow

from shallow water table, and irrigation must combine to meet his demand, while keeping rootzone

soil water potential (SWP) in the optimum zone. Otherwise, irrigation should be used to avoid water

stress. In the empirical relationship shown in (Figure 6.2), the objective of irrigation is to maintain

the soil water potential in the optimum zone and then ensure sufficient upward water flux to the

rhizosphere (Elmi et al., 2010; Caron et al., 2016). To achieve this, water may be added to the

system by either sprinkler irrigation, by maintaining an adequate water table depth or a combination

of both methods.

Sprinkler irrigation

In the past, sprinkler irrigation was typically turned on every other day through the cranberry

growing season without monitoring any of the soil-plant-atmosphere conditions. The recent findings

of Bonin (2009) that photosynthesis is maximized when SWP ranged from -4.0 to -6.5 kPa for

fruiting uprights and -1.0 to -4.0 kPa for vegetative stems, suggests that wet conditions could result

87

in vegetative growth instead of fruiting growth, and so more sophisticated control of irrigation and

of SWP might be beneficial.

While evaluating SWP values between -5.5 and -10.0 kPa for initiation of irrigation, Pelletier et al.

(2015a) found yield component reduction associated with thresholds lower than -7.5 kPa. The

number of marketable berries per fruiting upright and the number of fruiting uprights per unit area

were 14 and 21% lower, respectively, in the dry treatments (irrigation initiated at < -7.5 kPa). Final

yield, however, was reduced by 11% with this threshold (Pelletier et al., 2013). Irrigation should

then be turned on when SWP reach -7.5 kPa and avoiding water stress during fruit set and bud

development seems then to be of first importance. Using this threshold also reduced pumping up to

93% in comparison with wetter thresholds. Hydraulic models developed indicated so water flux

limitation for proper bottom-up water movement in that range (Caron et al., 2016).

Since yield heterogeneity over a cranberry bed could result from a large variability of SWP,

Gumiere et al. (2014) suggested managing irrigation in different zones inside one bed. However,

splitting a bed in several irrigation zones can be easy to manage for a small farm, but it could be

more complex, even impossible, to apply for larger farms with dozens or hundreds of beds. A

common conclusion to all the studies on sprinkler irrigation is that water table control could allow

to save more water and energy and improving the yield by reducing the cycling of SWP over time

in comparison with sprinkler irrigation (Bonin 2009; Pelletier et al. 2013; Gumiere et al. 2014;

Vanderleest et al, 2016b).

Water table control

Water table control has been tested for different crops and regions around the world and identified

as a best water management practice for reducing the environmental impact and maintaining or

enhancing crop yield (Evans et al., 1996; Madramootoo et al., 2001). Instead of supplying water

downward from the sprinklers to the rhizosphere, water is supplied by upward movement from the

water table to the rhizosphere. The WTD may be maintained by adding water by gravity from the

reservoir to the subirrigation inlet (drainage outlet) located in ditches, or by pumping. Compared to

sprinkler irrigation, lower pressure pumps can be used (Vanderleest et al. 2016b), reducing capital

and operating expenses.

For early rooting and vegetative growth, growth rate was greatest and rooting depth shallowest with

rooted cuttings grown in a greenhouse under WTD at 13 cm compared to 39 and 57 cm (Baumann

et al., 2005). Similar results were obtained with a WTD at 6 cm in comparison to 35 cm (Hall,

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1971). For established beds, based on the SWP-WTD relationships, crop water requirements could

be supplied through capillary rise with a WTD at 30–50 cm (Elmi et al., 2010), or 40–60 cm (Caron

et al., 2016); however, a very high risk of water stress for the crop could result from a WTD at 80

cm (Caron et al., 2016). Higher fruit yield resulted from a 30–38 cm WTD in three out of five years

when compared to 38-46 cm WTD and in four out of five years when compared to a 46-54 cm

WTD (Eck, 1976). However, these results were obtained prior to knowledge of the relationship

between SWP and yield. With water table control as the main water management method and

sprinklers (initiated when SWP reached -7.5 kPa) as a supplemental irrigation method, the highest

yields were obtained with WTD at 60 cm (Pelletier et al., 2015b). In that study, cranberries have

been identified to be very sensitive to WTD. Indeed, a WTD lower or higher by 30 cm than the

optimal depth (i.e. 30 > WTD > 90 cm) is associated with a yield decline of ~25%. This has been

explained by the reduction of the capacity of the plant to set fruit from flowers when WTD is not

optimal. Indeed, the number of berries per fruiting upright goes from two to one when WTD goes

from 60 to 75 cm. Moreover, higher yields were associated with higher fruit quality. Sugar content

(Brix), TAcy, total acidity (TA) and the ratio of Brix to TA, an indicator of the taste perception,

were higher when WTD was ~60 cm. Water table control was also beneficial from an

environmental point of view since water and energy saving reached 77%. Vanderleest et al. (2016b)

also found similar savings with WTD at 60 cm and established that a significant portion (about

30%) of the crop evapotranspiration was supplied from the water table. In order to maximize yield

and yield quality, and saving water and energy, water table should then be maintained at 60 cm

depth.

Cranberry beds should be constructed so that WTD can be controlled uniformly. For example, each

block of beds at the same elevation should be enclosed by deep ditches to ensure the uniformity of

the WTD. Indeed, as shown in Pelletier et al. (2015b), one meter difference level between two

blocks of beds resulted in 16% yield reduction between adjacent beds. Moreover, real-time

monitoring of the WTD is a prerequisite for growers for adjusting the water level in ditches. In

addition to pressure probes installed in observation wells, Vanderleest et al. (2016b) successfully

monitored WTD with tensiometers ~10 cm lower than the rooting depth. They found that SWP at

this depth was in hydrostatic equilibrium with the water table and so could be use to predict WTD.

A potential side effect of subirrigation is the risk of salt buildup at the soil surface and, considering

that cranberries roots are close to the surface, salt accumulation may be detrimental to crop growth.

However, little is known about cranberry tolerance to ion accumulation under field conditions. In a

greenhouse experiment, Samson et al. (2016) monitored salinity in two irrigation treatments after

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applying between 1 and 60 times the recommended dose of potassium to create important salt

stresses. Growth parameters showed a linear response to salinity levels while productivity

parameters had a quadratic response. For instance, photosynthesis declined by 22% and yield by

56% when electrical conductivity in the soil solution of 3.2 dS∙m-1 in comparison with 0.4 dS∙m-1

for the control treatment. The differences were greater for drier the treatment. They also found that

EC could be reliably monitored with a capacitive probe with no calibration or with a calibrated time

domain reflectometry probe (Samson et al, 2016).

6.2.2. Avoiding heat stress

High temperature is a major limiting factor in cranberry production (DeMoranville et al., 1996;

Degaetano and Shulman, 1987). Water table control may result in higher canopy temperature

compared to sprinkler irrigation since in the latter water is applied directly to the leaves, buds, and

fruits, and this water is likely cool compared to mid-day canopy temperatures. This cooling effect

may remain effective for a large part of the day. The risk of heat stress may then increase with the

use of water table control because of the increasing vapor pressure deficit near the foliage caused by

lower relative humidity in the bed as no water is applied overhead and therefore, and a higher

temperature. Consequently, plants may overheat under high evaporative conditions as stomata

gradually close to prevent water loss. A traditional cultural practice for avoiding overheating is to

turn on sprinkler irrigation a few minutes around midday for cooling the plants when a critical

temperature threshold is reached.

Maximum photosynthesis of fruiting uprights occurs at a leaf temperature of 25-29 °C (Pelletier et

al., 2016a). At 33 °C, photosynthesis was 11% lower and continued to decline at 37 °C with a

reduction of 22%. An earlier report (Kumudini (2004) showed slightly lower values of

photosynthesis (~2–3%) in cranberry runners exposed to 35 °C compared to 30 °C. Since fruiting

uprights are more important than runners for increasing yields, a temperature of 33 °C should be

used to trigger cooling irrigation. Cooling the vines led to a carbon gain of 19% and was efficient to

avoid midday depression (Pelletier et al., 2016a), a phenomena first reported in cranberries by

Hagidimitriou and Roper (1995), wherein photosynthesis peaked 2-3 hours after sunrise and

declined to ~50 % in the afternoon (Kumudini et al., 2004). Excessive irrigation for cooling has the

potential to stimulate unneeded vegetative growth, cause greater water loss, and leach nutrients, so

the practice should be limited to only one event per day. One irrigation episode of 20 minutes was

sufficient for cooling vines during 2-5 h (Pelletier et al., 2016a). Canopy temperature should be

monitored with radiation-shielded sensors to provide accurate readings.

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6.2.3. Avoiding frost damage

Developing cranberry buds can be susceptible to low temperatures in the spring, so frost protection

by irrigation is practiced (Workmaster and Palta, 2009). As irrigated water droplets freeze on the

canopy latent heat is released, keeping the bud temperatures above damaging temperatures.

Following a spring with 17 cold nights, Eaton (1966) found yield losses of 90% and a 15%

reduction in the size of berries on unprotected beds compared to protected beds. Major losses

occurred when the frost persists during only 1 h in unprotected beds (Sandler and DeMoranville,

2008). The temperature threshold at which protection must be initiated to prevent damage depends

on cultivar and growth stage. For example, with the ‘Stevens’ cultivar, the tolerance threshold is -5

°C at the cabbage head stage, -3 °C at the bud elongation stage, and -1 °C at hook and bloom stage

(Workmaster and Palta, 2009). Temperature sensors must be positioned at the top of the canopy,

several meters away from a dike and multiple sensors should be installed to take into account the

spatial variability of air temperature (Bryla, 2015). Indeed, temperature difference within a block of

beds may be by 2-3°C (Bryla, 2015). To reduce the amount of water that must be applied to afford

protection, automatic cycling of irrigation has been successfully tested in Massachusetts by

stopping water application when the temperature reaches 2°C higher than the initial trigger and

restarting when temperature dropped again below the initial trigger (Jerenamya et al., 2015). Trials

have shown a reduction of 30% of the amount of water applied and a significant yield increase with

the Stevens cultivar. Since a conventional frost protection night can saturate the soil, the yield

decrease in the non-cycled treatment could be due to the photosynthesis reduction under hypoxic

conditions (Pelletier et al., 2016b). The bed drainage system should allow to rapidly evacuate the

liquid water generated from melting ice following irrigation for frost protection (Pelletier et al.,

2016b).

6.2.4. Avoiding hypoxic conditions

Hypoxic conditions in the rhizosphere may result from 1) inadequacy of the drainage system to

remove the excess of water during and after a rainfall or a frost protection event or 2) a water table

maintained too close to the soil surface. The consequence of soil waterlogging depends on the

growth stage. Indeed, photosynthesis declined by 28% only after the first day of hypoxia during bud

elongation while the decline was significant only after the fifth day during fruit set, but

photosynthesis remained constant during fruit development even after five days of soil saturation

(Pelletier et al., 2016b). Using water table control increases the risk of hypoxia in the rhizosphere

after precipitation if the drainage system design is not adequate (Pelletier et al., 2015b). In a growth

cabinet, Laurent (2015) measured a photosynthesis reduction of 60-80% after an entire growing

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season with WTD maintained at 8-35 cm in comparison to a 60 cm depth. Laurent (2015)

concluded that the rate of the oxygen diffusive flux in the soil should be greater than about 0.4 mg

m-2 s-1 to avoid the detrimental effects of a lack of aeration.

Drainage problems limiting the evacuation of the excess water after a rainfall or irrigation for frost

protection event may induce significant yield limitations (Baumann et al., 2005). Indeed, a

significant yield reduction of 39 % was measured in organic cranberries where drain pipes were

fully clogged (Pelletier et al., 2016c). Cranberries stayed in dormancy until drain cleaning with a

pressure machine. In another study, a significant yield reduction of 25 % was subsequently

measured in half of the bed due to a drainage outlet installed closer than drain depth to the soil

surface (Pelletier et al., 2016c). The problem was corrected by moving the drainage outlet below the

drain depth and the year after this correction, the yield difference between the two parts of the bed

became non-significant the next year. These yield reductions may easily be explained by the high

cranberry sensitivity to hypoxic conditions (Pelletier et al., 2016b).

6.3. Conclusions and recommendations

Cranberry water management has improved in recent years through better understanding of water

and oxygen dynamics in soil, identifying significant plant stresses, the thresholds at which such

environmental stresses occur and designing strategies and tools for avoiding their detrimental

effects on final yields. Integrating the latest findings allows us to propose guidelines for a complete

irrigation management approach using available technologies (Figure 6.3). Using water table

control as the main water management strategy increases yield and saves significant water and

energy when the water table is maintained at a depth of 60 cm in a sandy soil. When the upward

flux from the water table becomes insufficient to meet the plants requirements, sprinkler irrigation

should be triggered at a soil water potential of -7.5 kPa for avoiding water stress. Because the

difference between the optimal SWP for initiating irrigation and SWP resulting in water stress is

very small (~1 kPa), the tensiometers used by the growers have to be very accurate. Buried

tensiometers should then be used for limiting the error associated with pressure fluctuations due to

air temperature changes (Warrick et al., 1998). Accurate equipment for monitoring soil water

potential may seem expansive, but has a payback period between 5 and 20 months, which varies

with farm size, cranberry price and rainfall (i.e. wet vs dry summer) (Jabet et al., 2016). The

optimal number of probes per unit area is on the variability of the beds, but typically reaches 1 per 4

ha for small operation and 1 for 8 in very large (400 ha operations), as reported by Jabet et al.

92

(2016). Additionally, electrical conductivity readings should be added for the management, as the

crop appeared sensitive to salinity (Samson et al., 2016) and buildup is at risk if subirrigation only

is used. On the long run additional, work on oxygen should be performed, as the crop appears

highly sensitive to aeration too (Laurent, 2015).

Sprinkler irrigation should also be turned on for 20 minutes in order to limit heat stress when the

temperature in the foliage reaches 33 °C, even if the soil water availability is sufficient. Monitoring

the temperature is also necessary in order to protect the plants against the frost. In this case, cycling

of water application can reduce the amount of water needed. Since hypoxic conditions in the

rhizosphere considerably reduce photosynthesis, the drainage system must be adequately designed

to rapidly remove water during frost protection and rainfall. Possible changes in the soil should also

be monitored in order to prevent and characterizing drainage problems.

Promoting best water management practices will help growers to attain maximum yields and reduce

water, fertilizers, pesticides and energy inputs. However, further research is necessary to assess new

recommendations based on the interaction of these inputs with new water management practices.

Improvement in water management may also hold potential for limiting root rot, diseases and

fungus propagule dispersion and development.

Figure 6.3. Guidelines for complete irrigation management approach using new technologies in cranberry production.

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6.4. Acknowledgements

The authors of this paper acknowledge the financial contribution of the Natural Sciences and

Engineering Research Council of Canada, Fonds de Recherche Nature et Technologies du Québec,

Nature Canneberge, Canneberges Bieler, Transport Gaston Nadeau, Hortau and the Scientific

Research and Experimental Development Tax Incentive Program of the Canada Revenue Agency

and Revenu Québec.

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6.5. References

Baumann, D. L., Workmaster, B. A., Kosola, K. R. 2005. ‘Ben Lear’ and ‘Stevens’ cranberry root and shoot growth response to soil water potential. HortScience. 40: 795-798.

Bonin, S. 2009. Régie agroenvironnementale de l'irrigation en production de canneberges (Vaccinium Macrocarpon Ait.). Master’s Thesis, Université Laval, Québec, QC, Canada.

Bryla, D. 2015. Temperature thresholds to freeze damage in cranberry in the maritime climate of western Oregon. North American Cranberry Researchers and Extension Workers (NACREW) Conference, Bandon, OR, USA, 2015 Aug. 24-26.

Caron, J., Bonin, S., Pepin, S., Kummer, L., Vanderleest, C., Bland, W. L. 2016. Determination of irrigation setpoints for cranberries from soil- and plant-based measurements. Can. J. Soil Sci. 96: 37-50.

Degaetano, A. T., Shulman, M. D. 1987. A statistical evaluation of the relationship between cranberry yield in New Jersey and meteorological factors. Agric. For. Meteorol. 40: 323-342.

DeMoranville, C. J., Davenport, J. R., Patten, K., Roper, T. R., Strik, B. C., Vorsa, N. Poole, A. P. 1996. Fruit mass development in three cranberry cultivars and five production regions. J. Amer. Soc. Hort. Sci. 121: 680-685.

DeMoranville, C., Kennedy, C., Neill, C., Jakuba, R. 2015. Cranberry nitrogen and the environment. North American Cranberry Researchers and Extension Workers (NACREW) Conference, Bandon, OR, USA, 2015 Aug. 24-26.

Eaton, G.W. 1966. The effect of frost upon seed number and berry size in the cranberry. Can. J. Plant Sci. 46: 87-88.

Eck, P. 1976. Cranberry growth and production in relation to water table depth. J. Am. Soc. Hortic. Sci. 101: 544–546.

Eck, P. 1990. The American cranberry. Rutgers University Press, New Brunswick, NJ.

Elmi, A., Madramootoo, C., Handyside, P., Dodds, G. 2010. Water requirements and subirrigation technology design criteria for cranberry production in Quebec, Canada. Can. Biosyst. Eng. 52: 1-8.

Evans, R. O., Gilliam, J. W., Skaggs, R. W. 1996. Controlled Drainage Management Guidelines for Improving Drainage Water Quality. Available online: http://www.bae.ncsu.edu/programs/extension/evans/ag443.html. (accessed on 15 September 2015).

FAOSTAT (Statistics division of the Food and Agricultural Organization). 2015. Cranberries - Production of top 5 producers. Available online: http://faostat3.fao.org/browse/Q/QC/E (accessed on 21 May 2015).

Gumiere, S. J., Lafond, J. A., Hallema, D. W., Periard, Y., Caron, J. Gallichand, J. 2014. Mapping soil hydraulic conductivity and matric potential for water management of cranberry: Characterisation and spatial interpolation methods. Biosystems Eng. 128: 29-40.

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Hagidimitriou, M., Roper, T. R. 1995. Seasonal changes in CO2 assimilation of cranberry leaves. Sci. Hort. 64: 283-292.

Hall, I.V. 1971. Cranberry growth as related to water levels in the soils. Can. J. Plant Sci. 51: 237–238.

Jabet, T., Caron, J., Lambert, R. 2016. Return on investment associated with irrigation strategies in cranberry production. Can. J. Soil Sci. (In Review).

Jeranyama, P., Ndlovu, F., Kennedy, C., DeMoranville, C. 2015. Temperature set-point effect on cranberry bud damage in frost cycling. North American Cranberry Researchers and Extension Workers (NACREW) Conference, Bandon, OR, USA, 2015 Aug. 24-26.

Kennedy, C. D., Kleinman, P. A. J., DeMoranville, C. 2015. Understanding phosphorous loss from cranberry farms. North American Cranberry Researchers and Extension Workers (NACREW) Conference, Bandon, OR, USA, 2015 Aug. 24-26.

Kumudini, S. 2004. Effect of radiation and temperature on cranberry photosynthesis and characterization of the diurnal change in photosynthesis. J. Am. Soc. Hort. Sci. 129: 106-111.

Laurent, T. 2015. Réponse de la canneberge (Vaccinium macrocarpon Ait.) à l’aération du sol. Master’s Thesis, Université Laval, Québec, QC, Canada.

Madramootoo, C. A., Helwig, T. G., Dodds, G. T. 2001. Managing water tables to improve drainage water quality in Quebec, Canada. Trans. Am. Soc. Ag. Eng. 44: 1511–1519.

Nolte, D. 2015. Industry trends and the importance of fruit quality for sweetened dried cranberry and fresh fruit production. North American Cranberry Researchers and Extension Workers (NACREW) Conference, Bandon, OR, USA, 2015 Aug. 24-26.

Pelletier, V., Gallichand, J., Caron, J. 2013. Effect of soil water tension threshold for irrigation on cranberry yield and water productivity. Trans. Am. Soc. Ag. Bio. Eng. 56: 1325-1332.

Pelletier, V., Gallichand, J., Caron, J., Jutras, S., Marchand, S. 2015a. Critical irrigation threshold and cranberry yield components. Agric. Water Manage. 148: 106-112.

Pelletier, V., Gallichand, J., Gumiere, S., Pepin, S., Caron, J. 2015b. Water table control for increasing yields and water savings in cranberry production. Sustainability. 7: 10602-10619.

Pelletier, V., Pepin, S., Gallichand, J., Caron, J. 2016a. Reducing cranberry heat stress and midday depression with evaporative cooling. Sci. Hort.198: 445-453.

Pelletier, V., Pepin, S., Laurent, T., Gallichand, J., Caron, J. 2016b. Cranberry gas exchange under short-term hypoxic conditions. HortScience. (Accepted).

Pelletier, V., Caron, J., Gallichand, J., Gumiere, S. 2016c. Impact of drainage problems on cranberry yields: Two case studies. Can. J. Soil Sci. 10.1139/CJSS-2015-0132.

Samson, M.-E., Fortin, J., Pepin, S., Caron, J. 2016. Impact of potassium sulfate salinity on growth and development of cranberry plants subjected to overhead and subirrigation. Can. J. Soil Sci. 10.1139/CJSS-2015-0111.

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Sandler, H. A., DeMoranville, C. J. 2008. Cranberry production: A guide for Massachusetts, summary edn. Cranberry Station - University of Massachusetts Amherst, Amherst.

Vanderleest, C. P. L., Bland, W. L. 2016a. Evapotranspiration from cranberry compared to the equilibrium rate. Can. J. Soil Sci. (10.1139/CJSS-2015-0093).

Vanderleest, C. P. L., Bland, W. L., Caron, J. 2016b. Water table level management as an irrigation strategy for cranberry (Vaccinium macrocarpon Aiton). Can. J. Soil Sci. (In Review).

Warrick, A.W., Wierenga, P.J., Young, M.H., Musil, S.A. 1998. Diurnal fluctuations of tensiometric readings due to surface temperature changes. Water Resour. Res. 34: 2863-2869.

Wilson, J. S. 2015. The cranberry institute – Research funding and MRL updates. North American Cranberry Researchers and Extension Workers (NACREW) Conference, Bandon, OR, USA, 2015 Aug. 24-26.

Workmaster, B. A., Palta, J. P. 2009. Frost hardiness of cranberry plant: A guide to manage the crop during critical periods in spring and fall. University of Wisconsin-Madison, Madison.

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CHAPITRE 7 Conclusion générale et perspectives futures

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7.1. Conclusion générale

Afin de demeurer compétitifs et de répondre aux nouvelles pressions de l’industrie demandant de

produire des fruits de qualité supérieure, les producteurs de canneberges devront utiliser des

pratiques culturales permettant de maximiser les rendements et la qualité des fruits tout en réduisant

l’impact environnemental de leur culture. Dans un contexte évolutif où les changements climatiques

entraînent une augmentation du nombre d’événements pouvant causer une contrainte au

développement optimal de la canneberge, le développement d’outils et de stratégies permettant

d’éviter les principaux stress environnementaux s’avère essentiel pour maximiser le rendement de

cette culture. Bien que les seuils critiques où surviennent ces stress soient bien connus pour

plusieurs espèces cultivées, ils demeuraient pour la plupart inconnus dans la production de

canneberge. L’objectif de cette thèse était donc de développer une approche intégrée de la gestion

de l’irrigation et du drainage en production de canneberges basée sur des outils technologiques

permettant le suivi en temps réel et à distance des conditions d’humidité du sol et de température de

l’air.

Le Chapitre 2 de cette thèse a permis de valider l’hypothèse selon laquelle l’utilisation du contrôle

de nappe combinée à l’irrigation par aspersion permet de maximiser les rendements et la qualité des

fruits tout en réduisant le volume d’eau et l’énergie nécessaires à l’irrigation. En effet, le rendement

final, la teneur en sucre, le nombre total de fruits, le nombre de fruits par tige et le taux de nouaison

ont été maximisés en évitant les stress hydriques par le maintien de la nappe à une profondeur

moyenne de 60 cm et en démarrant l’irrigation par aspersion lorsque la tension de l’eau dans le sol

atteignait 7.5 kPa. L’économie d’eau et d’énergie a par ailleurs atteint 77% lorsque la nappe était

inférieure à 66 cm. Lorsque la nappe était trop près de la surface du sol avant une précipitation, le

drainage était plus lent et entraînait des conditions hypoxiques dans la rhizosphère. Cependant, peu

d’informations étaient alors disponibles sur la tolérance de la canneberge à de telles conditions.

Dans le Chapitre 3, une expérience en cabinet de croissance a permis d’évaluer la durée maximale

que pouvait tolérer la canneberge en conditions hypoxiques. Dès le premier jour en conditions

saturées, la photosynthèse a diminué de 28%. Lorsque le sol de la rhizosphère était maintenu saturé

pendant plus de deux jours consécutifs, le taux de récupération de la photosynthèse après drainage

était supérieur à 10 jours. Ces résultats ont permis de démontrer que la canneberge est très

intolérante aux conditions hypoxiques et que le drainage doit être entièrement efficace afin de

permettre l’évacuation rapide de l’excès d’eau pendant une précipitation ou une nuit de protection

contre le gel.

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Le Chapitre 4 a permis de quantifier l’effet de certains problèmes de drainage sur le rendement de la

canneberge. Tandis qu’une conception inadéquate du système de drainage a entraîné une baisse de

rendement de 25% dans un premier cas, des drains colmatés par l’ocre de fer ont entraîné une perte

de rendement de 39% dans un second cas. Afin d’éviter les diminutions de photosynthèse se

traduisant par une perte de rendement lors de la récolte, le contrôle de nappe doit assurer un

drainage adéquat.

Avec le contrôle de nappe, l’air entourant le feuillage est généralement plus chaud et plus sec en

comparaison avec l’irrigation par aspersion, ce qui peut entraîner davantage d’épisodes de stress

thermique. Cependant, la température critique entraînant un stress thermique pour la canneberge

était inconnue.

Dans le Chapitre 5, une expérimentation en cabinet de croissance a permis d’identifier qu’en

comparaison avec une température optimale de 29 °C, la photosynthèse diminue de 11 % à 33 °C et

de 22% à 37 °C. Refroidir le feuillage pendant 20 minutes lorsque la température y atteint 33 °C

s’est alors avéré bénéfique pour éviter le stress thermique. Le refroidissement fut bénéfique même

lorsque le sol pouvait fournir l’eau nécessaire aux plantes, mais lorsque le sol était en conditions de

stress hydrique pour les plantes, le refroidissement était davantage bénéfique. Au champ, le

refroidissement a été efficace de deux à cinq heures suivant son application en fonction de certaines

variables environnementales. Plus la température de l’air et le vent étaient faibles et plus l’humidité

relative et le déficit de pression de vapeur dans l’air entourant le feuillage étaient élevés avant le

début de l’irrigation, plus cette irrigation était efficace.

Avant la réalisation de ces travaux de recherche, la gestion de l’eau en production de canneberges

était appliquée selon des règles empiriques. Avec l’étude des processus hydrologiques dominants

permettant de maintenir le sol dans la zone de confort hydrique de la plante (3.0-7.5 kPa) et de la

réponse physiologique de la canneberge aux principaux stress environnementaux, des stratégies

innovatrices permettant un transfert d’eau constant vers la rhizosphère et un certain contrôle sur le

microclimat entourant les vignes ont pu être développées dans cette thèse afin d’éviter ces stress et

permettre un rendement maximal. L’intégration de ces stratégies dans une nouvelle approche

intégrée de la gestion de l’eau en production de canneberges a été réalisée au Chapitre 6.

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7.2. Perspectives futures

La prochaine étape suivant l’application de cette nouvelle approche intégrée de la gestion de l’eau

en production de canneberges devrait être l’automatisation des procédés impliqués. Par exemple, le

démarrage automatique du système d’irrigation par aspersion lorsque les seuils critiques sont

atteints permettrait d’éviter les erreurs rattachées à la gestion manuelle des pompes. Le contrôle du

niveau d’eau dans les fossés entourant les champs pourrait également être automatisé afin d’ajuster

plus précisément la profondeur de la nappe dans les champs. En incluant les prévisions

météorologiques à l’algorithme décisionnel de gestion de l’eau, des irrigations inutiles pourraient

être évitées et le mode drainage pourrait être activé adéquatement lorsqu’une précipitation ou une

nuit de protection contre le gel est anticipée.

Afin d’améliorer l’uniformité de la profondeur de la nappe lors de son rabattement et lors de son

maintien par irrigation souterraine, la conception des systèmes de drainage pourrait être optimisée

en fonction des plus récents résultats de recherche. Ces améliorations pourraient permettre d’éviter

les conditions hypoxiques dans la rhizosphère tout en réduisant davantage le volume d’eau

nécessaire pour l’irrigation par aspersion.

Certaines pratiques culturales pourraient également être optimisées en fonction de la nouvelle

approche de gestion de l’eau. Par exemple, le taux et le moment d’application des fertilisants et les

besoins en pesticides pourraient être ajustés afin de maximiser davantage le rendement de la

canneberge.

101

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