Kamble et al. (2013) developed and validated equation to calculate Kc using NDVI based on regression analysis between NDVI derived from remotely sensed data and AmeriFlux measured crop coefficient under irrigated and rainfed crop condition for various crops. This equation can be used with Hargreaves and Samani equation to compute crop water requirement. There was a strong linear correlation between the NDVI-estimated Kc and the
measured Kc with an r2 of 0.91 and 0.90, while the root-mean-square error (RMSE) for Kc were 0.16 and 0.19, respectively for two different year in which experiments were carried out. Fig. 4 (b) shows the spatial variation of crop coefficient Kc, computed based on the equation: