Crop yield response to water - Cra
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Crop yield response to water - Cra

Crop yield response to water - Cra Crop yield response to water - Cra

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Figure 3 Relationships between relative yield and relative irrigation. Data correspond to regulateddeficit irrigation experiments carried out with Japanese plum cvs. Fortune, Black-Gold andBlack-Amber. The data from cvs. Black-Gold and Black-Amber were pooled together. All valuesare calculated relative to the fully-irrigated control plots.1.1Battilani 2004 Intrigliolo & Castel 2005 and 2010Naor et al. 20041.00.92y = -0.44x + 0.65x + 0.78r 2= 0.99Relative yield0.82y = -3.74x + 7.03x - 2.3r2= 0.810.70.60.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Relative irrigationwhereas in the study in Italy with the cv. Fortune, it was possible to reduce irrigation by 20-25 percent without any yield reduction. In addition, the response of Black-Gold and Black-Amber plums showed a much sharper decrease in relative yield with irrigation deprivationrelative to Fortune plums. The differences in the relationships between applied water and yieldare related to the unknown contribution of stored soil water and of in-season precipitation tothe crop ET c under water deficits. The similarity in the response of two different varieties inSpain and Israel probably reflect the limited contribution of soil storage in both studies (hencethe sharp decline in relative yield when irrigation decreases). Additionally, the differencesbetween the study in Italy and the other two might be the result of climatic conditions, withhigher winter and growing season precipitation in the Po Valley and tree age; mature trees inItaly and younger orchards in the studies in Spain and Israel.The patterns obtained in the above-mentioned studies are in line with general tree responsesto water supply, where yield increases with increasing water application but up to a pointwhere further increases in water application do not produce any increase in yield. Since thereare no studies relating yield to ET c in plum trees, overall data reported in Figure 3 showedthat for plum trees deficit irrigation could save around 10-20 percent of applied water withminimum or no yield loss.PLUM 353

Suggested Deficit Irrigation StrategiesThe suggested deficit irrigation strategy may greatly vary depending on the final marketproduct, dried fruit or fresh fruit, and on specific phenological aspects of each varietyaffecting bloom intensity and fruit set levels and particularly, earliness. The general strategyused to impose the water deficits for French prune was to limit water deficits during earlystages of tree and crop development, imposing more severe stress during mid and late season.In this sense, in a clay loam soil in California, allowing a progressive decline in midday SWPto approximately -1.5 MPa by harvest, e.g. irrigating at about 50-60 percent ET c from spring,resulted in an effective way to reduce irrigation and maintain an economic return over a3-year period (Lampinen et al., 2001a).For early season fresh market varieties it can be concluded that water stress after harvest thatlimits the decline in SWP below -2.0 MPa, despite some possible slight detrimental effect in thelong term, should be considered in commercial orchards not only for water scarcity, but alsoas a tool to control vegetative growth. In young orchards, postharvest deficit irrigation maybe combined with closer tree spacing, a feature very common in modern fruit tree plantationswhere new cultivars and orchards have a short life.For fresh market varieties water stress, if applied during fruit growth, should be concentratedduring pit hardening. The length of this phase depends on the harvest date. Hence, in earlyand even midseason maturing cultivars there is a risk of extending the water stress into thefinal fruit growth stage with detrimental effects on fruit size. Recent results (Intrigliolo andCastel, 2010) suggest that some degree of water stress can be applied during the early stageof fruit growth, providing that plant-water stress is mild (SWP > -1.4 MPa) and trees returnto optimum water status at least one month before harvest. The convenience of water stressapplied during fruit growth would indeed depend upon price market values of differentfruit size categories and fruit quality effects of water restrictions. In this sense it should beconsidered that deficit irrigation during fruit growth advances maturity, increases total solublesolids content and firmness, and may improve fruit colour. The effects of water restrictions onvolatile aroma compounds and particularly fibre and other fruit quality components relatedwith human health have not been extensively studied and could be of great importance forplum growers if the consumption of plums is promoted.354crop yield response to water

Figure 3 Relationships between relative <strong>yield</strong> and relative irrigation. Data correspond <strong>to</strong> regulateddeficit irrigation experiments carried out with Japanese plum cvs. Fortune, Black-Gold andBlack-Amber. The data from cvs. Black-Gold and Black-Amber were pooled <strong>to</strong>gether. All valuesare calculated relative <strong>to</strong> the fully-irrigated control plots.1.1Battilani 2004 Intrigliolo & Castel 2005 and 2010Naor et al. 20041.00.92y = -0.44x + 0.65x + 0.78r 2= 0.99Relative <strong>yield</strong>0.82y = -3.74x + 7.03x - 2.3r2= 0.810.70.60.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Relative irrigationwhereas in the study in Italy with the cv. Fortune, it was possible <strong>to</strong> reduce irrigation by 20-25 percent without any <strong>yield</strong> reduction. In addition, the <strong>response</strong> of Black-Gold and Black-Amber plums showed a much sharper decrease in relative <strong>yield</strong> with irrigation deprivationrelative <strong>to</strong> Fortune plums. The differences in the relationships between applied <strong>water</strong> and <strong>yield</strong>are related <strong>to</strong> the unknown contribution of s<strong>to</strong>red soil <strong>water</strong> and of in-season precipitation <strong>to</strong>the crop ET c under <strong>water</strong> deficits. The similarity in the <strong>response</strong> of two different varieties inSpain and Israel probably reflect the limited contribution of soil s<strong>to</strong>rage in both studies (hencethe sharp decline in relative <strong>yield</strong> when irrigation decreases). Additionally, the differencesbetween the study in Italy and the other two might be the result of climatic conditions, withhigher winter and growing season precipitation in the Po Valley and tree age; mature trees inItaly and younger orchards in the studies in Spain and Israel.The patterns obtained in the above-mentioned studies are in line with general tree <strong>response</strong>s<strong>to</strong> <strong>water</strong> supply, where <strong>yield</strong> increases with increasing <strong>water</strong> application but up <strong>to</strong> a pointwhere further increases in <strong>water</strong> application do not produce any increase in <strong>yield</strong>. Since thereare no studies relating <strong>yield</strong> <strong>to</strong> ET c in plum trees, overall data reported in Figure 3 showedthat for plum trees deficit irrigation could save around 10-20 percent of applied <strong>water</strong> withminimum or no <strong>yield</strong> loss.PLUM 353

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