Crop-weed competition and weed management studies in direct seeded rice (Oryza sativa)

Field experiments were conducted during 2006-07 and 2007-08 at Krishi Vigyan Kendra, Madurai, Tamil Nadu under the Zonal Project Directorate, Bangalore to study the critical period of crop weed competition and develop an integrated and effective weed control practices, combining chemical, manual and mechanical methods, for di- rect seeded rice ( Oryza sativa L.). It was found that first 40 days after sowing was the most critical period for crop weed competition. The crop grown under weed free condition for 40 days after sowing gave the maximum grain yield (2.93 t/ha). Hand-weeding followed by foliar application of urea was significantly superior to rest of the treat- ments and gave maximum grain (4.33 t/ha) and straw yields (8.17 t/ha). Post-emergence application of propanil @ 3.8 kg/ha at 20 days after sowing and soil application of urea was most effective in increasing the crop yield and minimizing the crop weed competition. Highest weed control efficiency of 88.1% was recorded in crop given propanil @ 3.8 kg/ha + hand weeding within rows and hoeing at 40 DAS and it closely followed by the application of butachlor @ 2.5 kg/ha + hand weeding within rows and hoeing at 40 DAS. In the integrated approach, post- emergence application of propanil @ 3.8 kg/ha at 20 days after sowing followed by hoeing between the rows and hand weeding within rows at 40 days after sowing minimized crop weed competition, increased uptake of N, P and K by crop and maximized grain yield and economical returns significantly.