Effect of integrated weed management practices on total weed dry weight, nutrient removal of weeds in rice-rice wet seeded system.

摘要

Field experiments were conducted in wet-seeded rice system during the kharif and rabi seasons of 1999 and 2000 in Madurai, Tamil Nadu, India. The main plot treatments consisted of rice-rice-fallow, rice-rice-summer ploughing, rice (green manure, GM)-rice (GM)-fallow, and rice (GM)-rice (GM)-summer ploughing; and the subplot treatments comprised weed management practices: pre-emergence application (PEA) of butachlor at 1.25 kg/ha followed by one hand weeding (HW) at 35 days after sowing (DAS), PEA of butachlor at 1.25 kg/ha followed by one HW at 35 and 55 DAS, presowing application (PSA) of glyphosate at 1.6 kg/ha+PEA of butachlor followed by one HW at 35 DAS, PSW of glyphosate+PEA of butachlor followed by one HW at 35 and 55 DAS, 3 hand weedings at 20, 35 and 55 DAS, and unweeded control up to 55 DAS. The major weeds in the experimental plots included Echinochloa crus-galli, E. colonum, Cyperus iria, Eclipta alba, Ludwigia parviflora and Marsilea quadrifolia. Intercropping of GM significantly reduced the total weed dry weight and nutrient removal by weeds compared to non-GM plots. When comparing the fallow with intercropping, summer ploughing with intercropping recorded the least. Regarding the weed management practices, the PSA of glyphosate, PEA of butachlor followed by one and 2 HW were at par with each other and significantly superior to all other treatments. At 35 DAS, HW treatment recorded the lowest dry weight and nutrient removal by weeds, however, this treatment was on par with the above treatments during the kharif season, and some variations were observed in the rabi season. Similar results were obtained at 55 DAS.