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This article in SSSAJ

  1. Vol. 52 No. 3, p. 849-855
     
    Received: Aug 6, 1987


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doi:10.2136/sssaj1988.03615995005200030045x

Nitrogen Use Efficiency and Nitrogen-15 Balances in Broadcast-seeded Flooded and Transplanted Rice

  1. S. K. De Datta ,
  2. M. I. Samson,
  3. Wang Kai-Rong and
  4. R. J. Buresh
  1. Department of Agronomy, Int. Rice. Res. Inst. (IRRI), P.O. Box 933, Manila, Philippines
    visiting scientist from the Int. Fertilizer Development Center (IFDC), P.O. Box 2040, Muscle Shoals, AL 35662

Abstract

Abstract

Increased irrigated areas, availability of short-duration modern rices (Oryza sativa L.) and cost-efficient herbicides, and high labor cost have motivated Asian farmers to shift from transplanting to broadcast seeding in flooded rice. Information on fate of N in broad-cast-seeded flooded rice (BSFR), however, in Asia is limited. Thus, two field experiments were conducted on a Vertic Tropaquept to evaluate efficient N management practices in BSFR using 15N-labeled fertilizers and to compare the performance of BSFR and transplanted rice (TPR) under similar N management practices. For urea, basal deep placement (DP) as supergranules and a three-split application gave the lowest mean 15N losses (4 and 11%, respectively) and highest mean grain yields (6.9 and 7.1 Mg ha−1, respectively) for BSFR. Mean 15N losses from urea applied to BSFR were 20 and 18%, respectively, for the researchers' split (RS) (two-thirds basally incorporated into mud plus one-third at 5 to 7 d before panicle initiation) and the farmers' split (FS) (one-half topdressed into water at 15 d and one-half topdressed at 10 d after panicle initiation). The agronomic efficiency (kg grain per kg applied N) for 40 kg applied urea-N was 57, 43, and 28 with DP, RS, and FS, respectively. Under the same urea management practices, the mean plant recovery of 15N was greater for BSFR (47%) than for TPR (37%). This resulted in lower 15N loss for BSFR (20%) than for TPR (32%). However, total plant N accumulation was similar for BSFR (96 kg ha−1) and TPR (95 kg ha−1), and mean grain yields over the two experiments were not different (P = 0.05) between BSFR and TPR. Transplanted rice produced 10 kg more grain per kilogram of applied N than did BSFR, in part because mean grain yield in the absence of applied N was 0.3 Mg ha−1 lower with TPR. Results suggest that considerable potential exists to increase N use efficiency and grain yield in BSFR by manipulating N fertilizer and water management practices.

Joint contribution from the IRRI and IFDC.

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