Effect of rice (Oryza sativa) culture, nitrogen and weed control on nitrogen competition between scented rice and weeds

A field experiment having 2 nitrogen levels (60 and 120 kg/ha), 5 weed-control treatments (weedy check, hand-weeding, butachlor 1.0 kg/ha, anilofos 0.5 kg/ha and chlorimuron ethyl 0.012 kg/ha) and 2 rice (Oryza sativa L.) cultures (direct seeded and transplanted) was conducted at New Delhi during the rainy season of 1993 and 1994. Intensity of competition for nitrogen increased with advance in age of crop and weeds. Weeds divested the crop of 43.0 kg M/ha in 1993 and 42.6 kg/ha in 1994 at maturity. At this stage weed control facilitated higher N uptake by the crop. Uptake of N in hand-weeding was 88.2 kg/ha in 1993 and 104.2 kg/ha in 1994, whereas it was only 57.6 kg/ha in 1993 and 54.1 kg/ha in 1994 in weedy check. Nitrogen uptake by crop at 120 kg N/ha was higher than at 60 kg N/ha in both the years. In transplanted rice culture, weed-control treatments were found approximately 4–18 times more efficient in arresting the N drain. In butachlor and anilofos, the N drain was relatively lower than chlorimuron ethyl. Hand-weeding was found more efficient in arresting N drain in both the cultures than herbicides.