Crop yield response to water - Cra

ox 19 (CONTINUED)(b) In the second case where fruit size determines the crop value, the price (redline) is negatively affected by the water deficits as water stress reduces fruit size,even more severely as the deficits intensify. Here, the revenue function (blue line) isdifferent and steeper than the yield function, thus favouring the application of highlevels of AIW at or very close to that needed to ensure maximum ET.b0Applied irrigation water2100Relativeyield %Relativerevenue%20050Relativeprice %11000Relative ET c10000achieve maximum ET c may also be the best for maximizing revenue. There are many possibilitiesthat can be effective for increasing the efficiency of water use when the supply is scarce, aspresented below.Irrigation system managementImproving the uniformity of water distribution over the field and maximizing applicationefficiency are two key goals that must be pursued in deficit situations. The goal is to eliminate,as much as possible, any unproductive water loss; to ensure that most of the applied wateris available for plant use. High application efficiency requires both good scheduling decisions(when to irrigate and how much water to apply) and irrigation systems designed and maintainedto achieve high uniformity. Lack of uniformity, when water is in short supply, might leaveareas in the orchard with supply levels so low that severe water stress could be induced. Themaximum attainable uniformity depends on the method of irrigation and it is difficult to exceed90 percent in practice, but it is critical to reach the highest possible level with any method used.An important consideration when irrigation scheduling with limited water is to exploit all thestored soil water available in the root zone of the tree so that the season ends with a dry soilprofile ready to be refilled by seasonal rainfall, in the geographical areas where this is feasible.288crop yield response to water