Crop yield response to water - Cra

Water Production FunctionsThe two primary yield components of citrus are fruit load and individual fruit weight. Visualappearance and the market values of different size fruit play a large role in determining thenet worth of a citrus crop, as they are in many tree and vine crops. This is illustrated with twoexamples from orange navels in the San Joaquin Valley, California (Goldhamer and Salinas,2000 and Goldhamer, 2007). The mean gross tonnage from the final three years of a fouryearexperiment where 13 different RDI regimes of various stress timings and durations wereimposed is shown versus applied water in Figure 2a. A linear expression fairly well describesthe relationship (R 2 =0.59) with a slope of about 2:1 in terms of reduced applied water: grosstonnage reduction. The primary difference in crop performance between the RDI regimes wasFigure 2(a) Crop, and (b) Gross revenue versus applied irrigation water for Frost Nucellar navels grownin the southern San Joaquin Valley of CA, USA. Data are mean values of the final three yearsof a four year RDI study (adapted from Goldhamer and Salinas, 2000).a484747Full irrigationGross fruit yield (tonne/ha)464645454444y = 0.0143x + 35.82R = 0.5991:1 Relationship43500550600650 700 750 800850Applied water (mm)b22 00021 50021 000Gross revenue (US$/ha)20 50020 00019 50019 000Full irrigation18 50018 0001:1 Relationship500550600650 700 750 800850Applied water (mm)324crop yield response to water