Water production functions for wheat under different environmental conditions

Water production functions have been developed in numerous forms; however, their transferability to widely different soils and climatic conditions is still a debatable subject. A study was conducted to evaluate the performance of existing evapotranspiration-yield functions for wheat with regard to their applicability and transferability under different environmental conditions in India. The functions were verified with data from field experiments conducted at a number of research stations located in different climatic regions of India. Depending on the nature of data input the functions were grouped into seasonal and growth stage functions. All functions were found to be statistically acceptable with regard to fitting available data. However, regression coefficients, i.e., yield response sensitivity factors varied in magnitude with the location of experiment even for the same wheat variety, which implies that the existing functions are site specific. Further the yield response sensitivity factor for the seasonal function was found to be dependent on site climatic and soil variables.