Effect of nitrogen and weed management in direct-seeded rice (Oryza sativa) under upland conditions

A field experiment was conducted during the rainy season of 2002 and 2003 at Sabour study the effect of nitrogen and weed management in direct-seeded upland rice (Oryza sativa L.). Grain and straw yields of rice and N, P and K uptake by rice crop and weeds increased significantly with successive increase in nitrogen up to 120 kg/ha. The splits in which basal application of nitrogen was skipped off resulted in significantly higher yield attributes, grain and straw yields and nutrient uptake by crop in comparison to splits wherein part of nitrogen was applied at sowing owing to lower weed dry weight and nutrient depletion by weeds that resulted in higher weed-control efficiency and N-use efficiency. Among the weed-management practices, 2 hand-weedings at 20 and 40 days after sowing and pre-emergence application of butachlor at 1.5 kg/ha + 1 hand-weeding at 30 DAS were at par; they significantly reduced the density and dry weight of weeds and nutrient depletion by weeds. These treatments significantly increased the nutrient uptake by the crop, resulting in higher grain yield (4.18 and 4.16 t/ha) of 120 kg N/ha as a result of higher weed-control efficiency (90.6 and 84.3%), N-use efficiency (33.5 and 32.9 kg grain/kg of N applied) and production efficiency (60.4 and 60.3 kg grain/kg N applied) respectively. However, minimum nutrient uptake by crop and miximum nutrient removal by weeds were noted under weedy check.