Most commercial blueberry (Vaccinium sp.) fields require a substantial amount of irrigation for profitable production. In the western United States, blueberry growers typically apply an average of 25–50 mm of water per week during the summer and up to 75 mm·week−1 during periods of peak water use (Bryla, 2011). However, many growers are facing serious water limitations due to warmer and drier weather conditions, increased regulations, and greater demand by other sectors (Dalton et al., 2013). For example, in 2015, blueberry growers in Oregon and Washington lost an estimated 14 million pounds of fruit due to heat and inadequate water for cooling and irrigation as a consequence of reduced water allotments from irrigation districts (Schreiber, 2016). This was more than a $20 million reduction in value to the industry. Growers in California are facing even more serious challenges due to an ongoing severe drought (Cooley et al., 2015). If water shortages continue to result in less water for irrigation, the total value of blueberry production and suitable farmland may be reduced substantially in the region.
Although it is difficult to predict how small fruit producers will attempt to mitigate for water shortages, long-term solutions might include drought-resistant cultivars and switching to more efficient irrigation systems and management methods. Many blueberry growers have already switched from using sprinklers to drip to increase irrigation efficiency, and are scheduling irrigation based on soil and weather conditions (Bryla, 2011). Additional strategies may include deficit irrigation or cutting off (stopping) irrigation at key developmental stages. Deficit irrigation is used successfully in many fruit crops, including peach [Prunus persica (L.) Batsch] and wine grape (Vitis vinifera L.), but it has not been well tested in berry crops (Chalmers et al., 1981; Fereres and Soriano, 2007; Goldhamer, 2007). The technique consists of restricting irrigation water applications during either a particular growth period or the entire growing season, without causing significant reductions in yield. Irrigation cutoffs may likewise be effective at reducing water use, provided the cutoffs occur during periods when water demands by the crop are low or less critical to fruit production. Preharvest irrigation cutoffs had no effect on yield in almond [Prunus dulcis (Mill.) D.A. Webb] and virtually eliminated hull rot at harvest (Goldhamer and Viveros, 2000). Previous work indicated that there may be analogous benefits to reducing preharvest irrigation in northern highbush blueberry (Bryla et al., 2009; Ehret et al., 2012, 2015). In this case, underirrigation by drip had no effect on yield in blueberry but increased fruit firmness and the content of sugar and acid in the berries, primarily as a result of a slightly smaller berry size.
Cropping thinning is also an effective strategy for dealing with soil water limitations in a number of fruit crops. For example, reducing crop loads during water deficits increased plant water status of peach (Lopez et al., 2006, 2010) and pear (Pyrus communis L.) (Marsal et al., 2008, 2010) and improved fruit quality of apple [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] (Mpelasoka et al., 2001; Neilsen et al., 2016). By thinning the crop when water is limited, competition for resources is reduced in the remaining fruit (Lopez et al., 2006; Proebsting and Middleton, 1980), resulting in larger fruit with better fruit quality and flavor (Crisosto et al., 1997; DeJong and Grossman, 1995; Wünsche and Ferguson, 2005). To avoid overthinning, thinning-intensity models have been developed according to the severity of water deficit for apple (Naschitz and Naor, 2005) and pear (Marsal et al., 2010). Similar models could easily be developed for blueberry, provided the strategy of reducing the crop load is cost-effective and actually mitigates reductions in production or quality under water-limited conditions. Thus, research is needed to determine whether there is any value to crop thinning during soil water deficits in blueberry.
The objective of the present study was to evaluate the potential of using deficit irrigation, irrigation cutoffs, and crop thinning to maintain yield and fruit quality with less water in northern highbush blueberry. Implementation of such strategies could result in immediate water savings and would enable growers and irrigation managers to optimize both on-farm and regional water use. Such information would be particularly critical in water-short years.
BertinN.GenardM.FishmanS.2003A model for early stage of tomato fruit development: Cell multiplication and cessation of the cell proliferative activityAnn. Bot. (Lond.)85741750
BrylaD.R.2011Crop evapotranspiration and irrigation scheduling in blueberry p. 167–186. In: G. Gerosa (ed.). Evapotranspiration – from measurements to agricultural and environmental applications. Intech Rijeka Croatia
BrylaD.R.GartungJ.L.StrikB.C.2011Evaluation of irrigation methods for highbush blueberry—I. Growth and water requirements of young plantsHortScience4695101
BrylaD.R.StrikB.C.2007Effects of cultivar and plant spacing on the seasonal water requirements of highbush blueberryJ. Amer. Soc. Hort. Sci.132270277
ChalmersD.J.MitchellP.D.Van HeekL.1981Control of peach tree growth and productivity by regulated water supply, tree density and summer pruningJ. Amer. Soc. Hort. Sci.106307312
CooleyH.DonnellyK.PhurisambanR.SubramanianM.2015Impacts of California’s ongoing drought: Agriculture. Pacific Institute Oakland CA
CosgroveD.J.1997Relaxation in a high-stress environment: The molecular bases of extensible cell walls and cell enlargementPlant Cell910311041
CrisostoC.H.JohnsonR.S.LuzaJ.G.CrisostoG.M.1994Irrigation regimes affect fruit soluble solids concentration and rate of water loss of ‘O’Henry’ peachesHortScience2911691171
DaltonM.M.MoteP.W.Snover (eds.)A.K.2013Climate change in the Northwest: Implications for our landscapes waters and communities. Island Press Washington DC
DeJongT.M.GrossmanY.L.1995Quantifying sink and source limitations on dry matter partitioning to fruit growth in peach treesPhysiol. Plant.95437443
DixonE.K.StrikB.C.Valenzuela-EstradaL.R.BrylaD.R.2015Weed management, training, and irrigation practices for organic production of trailing blackberry: I. Mature plant growth and fruit productionHortScience5011651177
EckP.1986Blueberry p. 75–85. In: S.P. Monselise (ed.). CRC handbook of fruit set and development. CRC Press Boca Raton FL
EckP.1988Blueberry science. Rutgers Univ. Press New Brunswick NJ
EhlenfeldtM.K.1998Enhanced bud production in highbush blueberry (Vaccinium corymbosum L.) in response to paclobutrazolHortScience337577
EhretD.L.FreyB.ForgeT.HelmerT.BrylaD.R.2012Effects of drip irrigation configuration and rate on yield and fruit quality of young highbush blueberry plantsHortScience47414421
EhretD.L.FreyB.ForgeT.HelmerT.BrylaD.R.2015Age-related changes in response to drip irrigation in highbush blueberryHortScience50486490
GoldhamerD.A.2007Regulated deficit irrigation in trees and vines p. 70–80. In: L. Hilliday (ed.). Agricultural water management. Natl. Academies Press Washington DC
GoldhamerD.A.ViverosM.2000Effects of preharvest irrigation cutoff durations and postharvest water deprivation on almond tree performanceIrr. Sci.19125131
Jorquera-FontenaE.AlberdiM.FranckN.2014Pruning severity affects yield, fruit load and fruit and leaf traits of ‘Brigitta’ blueberryJ. Soil Sci. Plant Nutr.14855868
KeenB.SlavichP.2012Comparison of irrigation scheduling strategies for achieving water use efficiency in highbush blueberryN. Z. J. Crop Hort. Sci.40320
KonarskaA.2015Development of fruit quality traits and comparison of the fruit structure of two Vaccinium corymbosum (L.) cultivarsScientia Hort.1947990
LiS.H.HuguetJ.G.SchochP.G.OrlandoP.1989Response of peach-tree growth and cropping to soil water deficit at various phenological stages of fruit developmentJ. Hort. Sci.64541552
LobosT.E.RetamalesJ.B.Ortega-FaríasS.HansonE.J.López-OlivariR.MoraM.L.2016Pre-harvest regulated deficit irrigation management effects on post-harvest quality and condition of V. corymbosum fruits cvBrigitta. Scientia Hort.207152159
LopezG.BehboudianM.H.VallverduX.MataM.GironaJ.MarsalJ.2010Mitigation of severe water stress by fruit thinning in ‘O’Henry’ peach: Implications for fruit qualityScientia Hort.125294300
LopezG.LarrigaudièreC.GironaJ.BehboudianM.H.MarsalJ.2011Fruit thinning in ‘Conference’ pear grown under deficit irrigation: Implications for fruit quality at harvest and after cold storageScientia Hort.1296470
LopezG.MataM.ArbonesA.SolansJ.R.GironaJ.MarsalJ.2006Mitigation of effects of extreme drought during stage III of peach fruit development by summer pruning and fruit thinningTree Physiol.26469477
MarsalJ.BehboudianM.H.MataM.BasileB.Del CampoJ.GironaJ.LopezG.2010Fruit thinning in ‘Conference’ pear grown under deficit irrigation to optimise yield and to improve tree water statusJ. Hort. Sci. Biotechnol.85125130
MarsalJ.MataM.ArbonesA.Del CampoJ.GironaJ.LopezG.2008Factors involved in alleviating water stress by partial crop removal in pear treesTree Physiol.2813751382
McCutchanH.ShackelK.A.1992Stem-water potential as a sensitive indicator of water stress in prune trees (Prunus domestica L. cv. French)J. Amer. Soc. Hort. Sci.117607611
MingeauM.PerrierC.AméglioT.2001Evidence of drought-sensitive periods from flowering to maturity on highbush blueberryScientia Hort.892340
MpelasokaB.BehboudianM.GreenS.2001Water use, yield and fruit quality of lysimeter-grown apple trees: Responses to deficit irrigation and to crop loadIrr. Sci.20107113
NaschitzS.NaorA.2005The effect of crop level on tree water consumption of ‘golden delicious’ apples in relation to fruit size: An operative modelJ. Amer. Soc. Hort. Sci.130711
NeilsenD.NeilsenG.GuakS.ForgeT.2016Consequences of deficit irrigation and crop load reduction on plant water relations, yield, and quality of ‘Ambrosia’ appleHortScience5198106
RiedererM.Müller (eds.)C.2006Biology of the plant cuticle. Blackwell Publishing Ltd. Oxford UK
SaftnerR.PolashockJ.EhlenfeldtM.VinyardB.2008Instrumental and sensory quality characteristics of blueberry fruit from twelve cultivarsPostharvest Biol. Technol.491926
SchreiberA.2016State of the Washington blueberry industry. 10 Aug. 2016. <http://whatcom.wsu.edu/ag/edu/sfc/documents/sfc2015/SchreiberBlueComm_SFC2015.pdf>.