Crop yield response to water - Cra

figure 18 The Main AquaCrop menu.displays on tab sheets for different aspect of crop, soil water and salt balance, the user canobserve and analyse a particular event on a specific parameter.Climate-Crop-Soil water is the most useful of the tab sheets (Figure 19). It displays three graphsplotted as a function of time: (i) depletion of root zone soil water (D r ), with the three water stressthresholds represents by lines of different colours; (ii) the corresponding progression of greencanopy cover (CC), with the potential CC (no stresses) shaded gray; and (iii) the transpiration (Tr)of the canopy (for the simulated CC size), with potential Tr shaded gray. On top of the menu thebiomass and yield are displayed along with the status of the water, temperature, soil fertilityand salinity stresses. The graphs vividly show how canopy expansion and transpiration areaffected when the absence of rain and irrigation led to drops in root zone water content belowthe threshold (green line, bottom graph) affecting canopy expansion, below the thresholdfor stomata (red line) affecting Tr, and below the threshold (yellow line) triggering canopysenescence. The reversal effects of water supply or irrigation are also obvious in the graphs.One feature of the Simulation run menu is particularly helpful to users seeking to develop aregulated deficit irrigation schedule to optimize water use. By selecting short simulation timesteps (1 to 3 days), a chosen amount of irrigation can be specified on the upper left panelat any time step (and date) during a simulation run, allowing quick and close scrutiny of theresultant benefits in the context of irrigation time, frequency, and amount. For more details,see Section 3.3 and the AquaCrop Reference Manual (Raes et al., 2011).AquaCrop: concepts, rationale and operation 47