SPATIAL VARIABILITY IN SEASONAL CROP EVAPOTRANSPIRATION AND MOISTURE STRESS FUNCTIONS

Abstract

The seasonal crop evapotranspiration (Et ) for wheat, cotton and sugarcane crops was used to estimate variability in seasonal Et and potential yield for major climatic zones. The average seasonal crop Et varied between 353-562, 587-797 and 1195-1482 mm for wheat, cotton and sugarcane crops, respectively, for major climatic zones. The variability in seasonal crop Et for various locations was highly significant for wheat and cotton and nonsignificant for sugarcane. Same trend was observed for potential yield. Seasonal crop Et - moisture stress functions were developed for wheat and cotton crops representing 50, 75 and 95% soil moisture depletion. Average water use efficiency for wheat and cotton crops is presented for number of locations. Water use efficiency was increased with the increase in soil moisture stress as irrigation timing criteria of 75 and 95% from that of 50%. Crop coefficients for wheat and sugarcane were affected by moisture stress especially during the peak water requirement period. This indicates the need to adjust crop coefficient with moisture stress because actual crop Et is reduced with the increase in soil moisture stress.