Studies on drip irrigation, fertigation and spacing in Bt cotton

Abstract

Three experiments were conducted to find out suitable crop geometry under drip irrigation, optimum irrigation schedule and optimum fertigation schedule for Bt cotton at Agricultural Research Station, Sriganganagar during Kharif 2009 to 2011. Paired row spacing of 60 X 120 cm & single row spacing of 90, 108 and 120 cm gave statistically at par seed cotton yield. When the row spacing of cotton was further increased to 135 cm, the yield of cotton was significantly reduced as compared to other closer row spacings tested in the study. The minimum drip cost was observed in paired row of 120 x 60 cm. Thus, 120 x 60 cm paired row spacing was found optimum for Bt cotton. The maximum seed cotton yield was recorded when drip irrigation was scheduled at 1.2 ETc, however, it was at par with seed cotton yield obtained at 1.0 ETc. Seed cotton yield at 0.8 & 0.6 ETc was significantly less than that of 1.0 & 1.2 ETc treatments. Thus, drip irrigation to Bt cotton at 1.0 ETc was found optimum. This treatment gave 31.0 % higher seed cotton yield and saved 32.9 % of irrigation water over conventional flood irrigation. The water expense efficiency was higher in the drip-irrigated treatments as compared to flood irrigation. The maximum water expense efficiency of 4.21 kg/ha mm was recorded at 1.0 ETc followed by 3.98 kg/ha mm at 0.8 ETc irrigation treatment with drip system. The maximum seed cotton yield was recorded at 120% RD of fertilizers, however, it was at par with 100% and 80% RD of fertilizer with 2% KNO3 spray. Thus, 80% RD of NPK+ foliar spray of 2% KNO3 at 90 and 105 DAS was found optimum for Bt cotton. This treatment gave 15.6 % higher seed cotton yield over conventional method of fertilizer application and irrigation. The maximum water expense efficiency of 3.95 kg/ha mm was recorded with120% of RD, followed by 3.87 kg/ha mm with100% of RD+2% KNO3 as foliar spray at 90 & 105 DAS and 3.78 kg/ha mm with 80% of RD +2% KNO3 as foliar spray at 90 & 105 DAS.