Crop yield response to water - Cra

FIGURE 5Relation between the crop coefficient (K c ) for drip-irrigated peach trees measured in aweighing lysimeter in central California and the proportion of light interception by the trees.The linear equation approximation to calculate the K c is:K c = 0.082 +1.59 (PMLI) (Ayars et al., 2003)1990 1991 1992 199319941.61.41.21Kc0.80.60.40.200 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8Proportion midday light interceptionconcluded that applied water may be reduced by 10- 20 percent below the maximum needswithout a negative impact on yield. However, the analyses have very seldom included revenueconsiderations, relative to the price differential that different sized peach fruit fetches inthe market. The response to applied water depends on the water storage capacity of thesoil, and thus cannot be generalized. Figure 6 shows the relation between yield and ET c inrelative terms for different irrigations strategies, full irrigation (Control), RDI, and sustainedDI (SDI). For the optimal RDI regime, it is possible to reduce the ET c by 15-20 percent withouta detrimental impact on yield. However, when the water deficits were imposed on sensitivestages or throughout the season (SDI), a reduction in ET c was accompanied by a yield reduction(Figure 6). The differences in the responses to the various DI regimes illustrate the benefits ofstress management when planning deficit irrigation programmes.SUGGESTED RDI REGImESBased on the results shown above, it can be concluded that RDI strategies applied duringStage II in peach, especially when a fast recovery at the beginning of Stage III can be achieved,has proved to be very effective in controlling excessive vegetative growth and improving fruitquality without a yield penalty. For early season cultivars, RDI that concentrates the waterdeficits in the postharvest period is an effective strategy, provided severe water stress isavoided (Tables 2 and 3). Given the impact that different root zone water storage capacitieshave to the response to RDI, Tables 2 and 3 present different RDI schedules for two types ofsoils (shallow and deep), also giving indications of the minimum stem-water potential treescan withstand without having a detrimental effect on yield.peach 403