The productivity of Bt. cotton in Tungabhadra Project of Karnataka state was high (80 percent) in left bank canal area compared to that in right bank canal area.  These differences in productivity of Bt cotton were attributed mainly due to variations in soil types and soil factors such as clay and organic carbon content and cation exchange capacity.  The ESP values above 10 were found to reduce cotton yields considerably due to dispersion of soil collides leading to surface encrustation, poor aeration and moisture limitation  Among major nutrients, phosphorus was more critical than nitrogen and potassium.