Field experiments were conducted during winter 2006-07 and 2007-08 at Tamil Nadu Agricultural University, Coimbatore to find out the effect of drip irrigation on the productivity and water use efficiency in Bt-cotton ( Gossypium hirsutum L.). The experiments were laid out in a randomized block design replicated four times. The treatments consisted of drip irrigation at 0.40, 0.60, 0.80 and 1.0 ET c (Crop evapotranspiration) compared with farmers' method (flood irrigation method). The results revealed that application of water to Bt-cotton through drip resulted in better growth, higher seed cotton yield and better quality of lint than the surface method. The yield advantage due to different irrigation schedules through drip based on ETc was 26.2 and 12.8% over surface method during 2006-07 and 2007-08, respectively. Among the irrigation through drip, irrigation at 0.80 ET c recorded better growth and gave higher seed cotton yield than irrigation at 0.60 ET c. The water use efficiency with drip irrigated Bt-cotton was 44.4% higher than the flood method of irrigation.
