Estimation of Crop Evapotranspiration of Cotton using Remote Sensing Technique

Crop coefficient values are used to estimate crop evapotranspiration (ETc) for determining irrigation scheduling. Many important crop biophysical properties such as Percentage Vegetation Cover and Leaf Area Index can be estimated from remotely sensed Vegetation Index, in order to quantify real time vegetation growth dynamics. The objective of this study was to understand the effectiveness of basal crop coefficient (Kcb) values estimated from remote sensing and their application in real time crop water requirement. The study was carried out for Cotton crop in Sirsa district of Haryana. Spectral index such as SAVI (Soil Adjusted Vegetation Index) and Fractional Vegetation Cover (Fc) were used to estimate Kcb value. High spatial resolution Landsat TM5 images were used to generate spectral profile of NDVI, SAVI and Fc for different crop cover. Using, available empirical models from literature, crop coefficient was derived from SAVI values. Reference Crop Evapotranspiration (ET0) was estimated using Blaney-Criddle Method, taking weather data from ICAR Research Station Observatory. The crop coefficients derived from Remote Sensing data were used along with ET0 values to estimate crop evapotranspiration (ETc). The result showed that the spatial distribution of seasonal ETc varied between 317 to 534 mm for growing season of cotton depending upon sowing date and other condition. The estimated crop evapo-transpiration (ETc) pattern was compared with fractional vegetation cover. Spatial distribution map of cotton ETc, basal crop coefficient and fractional vegetation cover showed areas of high and low water demand. This work can help in water management practices for better irrigation management. S.K. Singh et al 524