Nitrogen fertilizer and weed management in rainfed transplanted IR64 rice [Philippines]
1989
Llagas, M.A. | De Datta, S.K. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Efficiency of different N fertilizer management practices were evaluated under three weeding regimes in rainfed transplanted IR64 rice (Oryza sativa L.). Amount and time of N fertilizer application were varied while maintaining a total application rate of 80 kg N/ha as urea. Butachlor and two handweedings decreased total weed weights as compared with the untreated check. Handweeding gave lower weed weight than did the butachlor treatment. Although tiller count at 47 days after transplanting (DAT) was higher in handweeded than in butachlor-treated plots, leaf area index (LAI) and grain yield were similar under both weeding regimes. Fertilizer N application gave taller plants than did the no fertilizer N treatment. Among the N treatments, 3 equal splits of N-applied basally, at 20 DAT, and at 7 days before panicle initiation (DBPI)-- produced the tallest plants but were similar to those applied with 1/3 N at 20 DAT and 2/3 N at 7 DBPI. When weeds were not controlled, 2-split N application, where 1/3 N was applied 20 DAT and 2/3 N at 7 DBPI, and all of N applied at 7 DBPI produced more rice tillers. Without weed control, grain yields were similarly low regardless of N management level. When weeds were controlled, 3-split N applications consistently produced higher yields than did the nonfertilized plots. Single dose or 2-split N applications gave yields similar to those with no fertilizer N applied
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