Effect of different weed management practices on the yield and economics of irrigated cotton

摘要

Weeds in cotton crop is a major production constraint. In cotton, the critical period of weed competition prevails upto 60 to 75 DAS and during this period the crop needs weed free condition for better results (Thind et al. 1995). It is common practice with the farmers to take up manual weeding and frequent intercultivation in cotton. But, scarcity of labour and high soil moisture conditions due to frequent irrigation or heavy rains make the farmers unable to take up timely cultural practices including hand weeding, besides such operations are time consuming, expensive and tedious. Hence, it is necessary to find out alternate and appropriate weed control methods. Field experiments were conducted during winter seasons (August - February)of 1998-1999 and 1999-2000 at Tamil Nadu Agricultural University, Coimbatore. The following 13 treatments were laid out in a randomized block design with three replications: T_1-Control, T_2-Hand Weeding (HW) twice 20 and 40 DAS, T_3-Pendimethalin 1.0 kg ha~(-1) +HW, T_4-Cinmethylin 0.5 kg ha~(-1) T_5-Cinmethylin 0.5 kg ha~(-1) + HW, T_6-Cinmethylin 0.6 Kg ha~(-1), T_7-Cinmethylin 0.6 kg ha~(-1) + HW, T_8-Parthenium incorporation at 2 t ha~(-1), T_9-Parthenium whole plant extract spray (10 percent), T_(10)-Parthenium incorporation at 2 t ha~(-1) T_(11)-Parthenium whole plant extract spray (10 percent HW, T_(12)-Cowpea as smother intercrop upto 40 DAS, T_(13)-Pearl millet as smother intercrop upto 40 DAS and T_(14)-Greengram as smother intercrop upto 40 DAS. Thesoil was sandy clay loam with low (187.6 kg ha~(-1)), medium (14.0 kg ha~(-1)) and high (420.1 kg ha~(-1)) available nitrogen, phosphorus and potassium, respectively. The pH of the soil was 7.9 with an organic carbon content of 0.42 percent. The herbicides were applied as pre-emergence after sowing, followed by immediate irrigation. The cotton cv. MCU5 was sown at 75X30 cm spacing and supplied with 80:40:40 kg of NPK ha~(-1) respectively. Observation on weed count, number of sympodial branches plant~(-1), number of bolls plant~(-1) and seed cotton yield were made. Based on the yield and cost of cultivation, net return and Benefit cost ratio were worked out.