Crop yield response to water - Cra

notice that this was the case for Blanquilla for RDI-SII in Spain and also for the mild irrigationreductions in the Spadona experiment in Israel (Figure 3). However, this was not found to beso Conference, because RDI-SII, besides increasing blooming return, it also reduced fruit setthe next season so that competition between fruit was lowered. Specificity of cultivar yieldresponse to ET deficits could be explained by a different sensitivity of fruit set to current bloomdensity and past history of water stress. On the other hand, the advantageous yield responseobserved in Blanquilla was lost when analysed in terms of relative revenue (Figure 6). This wasbecause of the price penalty related to the production of smaller fruit under deficit with highcropping conditions (Figure 6). Therefore Conference and Blanquilla revenue responses wereapproximated by only one boundary line, which corresponded to the conditions of deficitirrigation applied during the fruit-growing season (Figure 6).In the case of postharvest deficit irrigation for Conference, it was found that relative revenuesrose above the boundary line (Figure 6). Curiously, postharvest water deficit produced yieldreductions that were accompanied by reductions in fruit set and associated with increased fruitsize. Accordingly, postharvest RDI fruit received a higher price and relative gross revenue wasnot reduced by the slight ET c reductions attained in the above-mentioned experiment (Figures5 and 6). However, under more significant stress during Stage II, which caused a 30 percentreduction in ET c , the decrease in gross revenue of the cv. Conference reached 60 percent(Figure 6), a response that is substantially more negative than what could be predicted fromthe yield-ET c relationship (Figure 5).Suggested RDI RegimesConsistency of results across the different experiments on RDI suggests that this techniquemay be safely used for pear production. However, the myriad of possible combinations ofpear growing conditions (cv. x rootstock x planting density x fruit load x soil type x climate)offer a wide spectrum of possibilities that have not been fully investigated in relation toRDI. Nevertheless, there is no doubt that, in climates having low rainfall during the hotseason, reducing irrigation during Stage II should be avoided to guarantee maximum fruitsize at harvest (Figure 6). Early water stress should also be avoided in most cases, except forhigh‐density orchards growing under vigorous conditions. The period in which RDI could beapplied to save water is postharvest, provided excessive water stress is not achieved. This riskof applying too much water stress during postharvest may depend on each specific situation.Risks increase where growing conditions are suboptimal. Bad weather can affect pollinationand fruit set, and fruit drop can occur especially during late spring. Postharvest water stresshas been hypothesized to reduce winter reserves in the tree (no data available on pear) andsubsequently impair fruit set and yield following season.The data available on responses to RDI make it difficult to propose a strategy that is applicableto all possible combinations of management practices. Nevertheless, the postharvest periodis the safest to apply RDI, but water savings can be short if a late maturing cultivar is used.Therefore, if water shortages have to be more severe, RDI could be applied in combinationwith other periods. Table 2 presents various RDI strategies for different water allocations thatare simulated for specific experimental and environmental conditions (Marsal et al., 2008;and Marsal et al., 2010). Water deficit in Stage I (RDI-SI), only allows a 6 percent reduction ofthe annual applied water. By using RDI in Stage II (RDI-SII), 33 percent of applied water can386crop yield response to water