Crop Yield Response To Water

CROP YIELD RESPONSE TO WATER
Food production and water use are inextricably linked. Water has always been the main factor limiting crop production in much of the world where rainfall is insufficientto meet crop demand. With the ever-increasing competition for finite water resources worldwide and the steadily rising demand for agricultural commodities, the call to improve the efficiency andproductivity of water use for crop production, to ensure future food security and address the uncertainties associated with climate change, has never been more urgent.
To examine the pathways forincreasing the efficiency and productivity of water use, the yield response of crops to water must be known. This relationship is complex in nature and various attempts have been made to provide simplified,though sound, approaches to capture the basic features of the response.
FAO’s first publication that presented a relationship between crop yield and water consumed was Irrigation and Drainage PaperNo. 33 Yield Response to Water (Doorenbos and Kassam, 1979). This approach is based on one single equation relating the relative yield loss of any crop (either herbaceous or woody species) to therelative reduction of water consumption, i.e. evapotranspiration, by way of a coefficient (ky), which is specific for any given crop and condition. This approach has provided a widely-used standard forsynthetic water production functions, still in use today. This simplification, however, made this approach more suitable for general planning, project design and rapid appraisal purposes, oftenproviding a first-order approximation. Over the last three and half decades, new knowledge has enlighten processes underlying the relationship between crop yield and water use and technology has improved.Further, novel needs have emerged related to the planning and management of water in agriculture, including those arising from climate change. FAO has, therefore, revisited the approach to quantify...