Journal of Agriculture and Forestry University, Volume 1 (2017) 89 Research Article ECOLOGICAL WEED MANAGEMENT PRACTICES AND SEED BED PREPARATION OPTIMIZED THE YIELD OF DRY DIRECT SEEDED RICE IN SUB-HUMID CONDITION OF CHITWAN, NEPAL S. Marahatta 1 *, S. K. Chaudhary 2 , P. Gyawaly 3 , S.K. Sah 1 and T.B. Karki 3 1 Agriculture and Forestry University, Rampur, Chitwan, Nepal 2 HKI, Kathmandu, Nepal, 3 Nepal Agriculture Research Council ABSTRACT The weeds are a major constraint of dry-direct seeded rice (DDSR) due to change in establishment methods and shifting weed fora towards competitive grasses and sedges. For optimizing the yield of DDSR through environmental friendly weed management practices, two feld experiments were conducted during the monsoon season of 2014 on Chitwan, Nepal. First experiment was done using a strip plot design to fnd the optimum seed rate and killing date of sesbania under rice- sesbania co-culture whereas the second experiment was done by using a split plot to observe the effciency of stale seed bed for weed control and to identify the best integrated weed management practice. The optimum seed rate of sesbania was 102 kg ha -1 and killing dates was 32 days. The sesbania co-culture with 100 kg ha -1 when killed at 28 days had produced signifcantly higher grain yield than sole Bispyribac Na application, and only 4.79% yield was loss than farmers’ practice of two hand weeding. In contrary to weed free, Pendimethalin followed by Bispyribac Na application and Pendimethalin followed by 2,4-D application produced statistically similar yield followed by sesbania co-culture with 100 kg seeds and killing at 28 days. During the monsoon rice, the effectiveness of stale seed bed was not much greater (0.37%) than the normal seed bed. Key words: hand weeding, sesbania co-culture, stale seed bed, weed index INTRODUCTION The national average yields of rice in Nepal (3.17 t ha -1 ) is far below the attainable yield of 5.00 t ha -1 (FAO, 2014; Dey, and Hossain, 1995) consisting the yield gap of 1.83 (57.73%). Conventionally rice is cultivated by transplanting of 20-30 days seedlings after puddling. Puddling have advantages of reducing weed population (Surendra, Sharma, Rajendra, Singh, & Prasad, 2001), enhancing nutrient uptake by creating anaerobic condition, higher water use effciency by reducing the evaporation and percolation loss, facilitate transplanting and easy seedling establishment (Sanchez, 1973). But it adversely affects soil physical properties by dismantling soil aggregates, reducing permeability in sub-surface layers (Sharma,Ladha, & bhushan, 2003), forming hard pans at shallow depths which hinders the root development of non-rice crops grown in rice based cropping system and greater emission of methane gas in atmosphere contributing global warming (Tripathi, Sharma, & Singh, 2005) and urged for substitutes. Dry-DSR gaining popularity regarding its high water use, labor use and energy use effciencies * Corresponding author: santoshmarahatta@gmail.com : 89-101