Crop yield response to water - Cra

ox 7Consumptive and non-consumptive uses of water.Water may be used beneficially for irrigation if used considering ET c for salt leaching or forfrost protection. Irrigation efficiency (IE) is the ratio of beneficial to non-beneficial uses ofwater. Also shown are the various consumptive and non-consumptive uses of water.• Crop ETc• Evaporation for frostprotection or for cooling• Deep percolationfor salt leachingBenef.UsesIE%100%• Weed & Phreatophyte ET• E from spray jets• E from soil, reservoirs& canals• Excess deep percolation• Excess runoff• SpillsNon-Benef.Uses(100-IE)%ConsumptiveUseNon-ConsumptiveUseBox 8 illustrates how the distribution of irrigation water varies in different parts of the field;in some, it exceeds the required depth, while in others it is less than required. The shaded areaindicates the degree of deficit in the field. This deficit could be reduced or even eliminated byapplying a gross irrigation depth in excess of that required, leading to more deep percolationlosses. Systems with high DU have water distribution lines in the Figure of Box 8 that are closeto horizontal, with little water excess and deficit, while lower DU values cause the line to besteeper (more variation among sites within the field) and hence there will be greater lossesand deficits in the field.In order to calculate the gross irrigation requirement (GIR) of an orchard or vineyard, thecomputed ET c , which is considered as the net irrigation requirement (NIR), should be dividedby the application efficiency (AE), as:(11) GIR = NIR / AEWhere AE is expressed as a fraction.This effectively increases the net irrigation amount by an amount determined by the applicationefficiency. For example, an application efficiency of 80 percent requires that 20 percent morewater than the ET c is applied to the field. Knowing the system application efficiency is just asimportant as knowing the ET c when calculating irrigation requirements. It would be uselessto devote effort to calculate precisely calculating the ET c and then not pay attention to theactual delivery process to the field and the degree of uniformity of the irrigation system.Yield Response to Water of Fruit Trees and Vines 269