Impact of Weed Management Practices on Biomass and Grain Yield of Two Varieties of Paddy in Lowland Area of Far-Western Nepal

Experiments were conducted in two varieties of transplanted paddy (cv. Radha-4 and Neemai) during the rainy season of 2004-2005 in the Far-Western Terai region of Nepal to assess the effect of weed management practice. Four experiments were conducted in randomized block design with three replications viz. unweeded (T 0 ), weed free (TT), manured plus twice hand-weeded after 25 and 50 days of transplanting (T 1 ), and chemical fertilizer plus butachlor (weedicide) application (1.5 kg ha -1 ) (T 2 ). A total of 48 weed species were identified with densities of 208 ind. m -2 in Radha-4 and 196 ind. m -2 in Neemai. The mean maximum biomass of paddy in weed-free plots were 3553.6 and 3588.4 g m -2 in Radha-4 and Neemai respectively. This biomass was more or less similar to twice hand-weeded plots and herbicide treated plots being 1.3% lowering in both the varieties, compared to weed-free plots. Compared to weed-free plots, the biomass reduction in unweeded plots was recorded 26.1% lower in Radha-4 and 26.3% in Neemai. The weed biomass was recorded highest in unweeded plots (296.9 and 236.2 g m -2 ) and lowest 155.7 and 109.1 g m -2 in twice hand-weeded plots. The trend of grain yield in both the varieties were: weed free (TT) > manured plus twice hand-weeded after 25 and 50 days of transplanting (T 1 ) > chemical fertilizer plus butachlor application (1.5 kg/ha) (T 2 ) > unweeded (T 0 ). Key words: Rice; Weeds control; Western Terai; Biomass DOI: 10.3126/njst.v9i0.3157 Nepal Journal of Science and Technology 9 (2008) 15-20