Predicting Effects of Water Shortage on Crop Yield

This paper discusses the relationships existing between water use (expressed as evapotranspiration) and yields of alfalfa, wheat and grain sorghum. Data, assembled from a number of sources, is used to tentatively formulate water production functions in both absolute and relative forms. A detailed hypothetical example of use of such a function for water allocation and management planning for maximization of wheat production during a water shortage is given. The example serves to put into perspective the disproportionate importance which can attach to stored soil moisture and in-season precipitation when maximization of total production is the goal. Conclusions are basically that definition of water use-yield relationships can be done for certain crops from experimental data extant, and that the functions thus produced would greatly assist planners at all levels in making water allocation and management decisions, particularly in situations of water shortage.