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This article in SSSAJ

  1. Vol. 56 No. 5, p. 1521-1527
     
    Received: Oct 15, 1990
    Published: Sept, 1992


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doi:10.2136/sssaj1992.03615995005600050031x

Seasonal Accumulation and Partitioning of Nitrogen-15 in Rice

  1. D. Guindo,
  2. B. R. Wells,
  3. C. E. Wilson and
  4. R. J. Norman 
  1. Dep. of Agronomy, Univ. of Arkansas, Fayetteville, AR 72701
    Univ. of Arkansas Rice Research and Extension Center, Stuttgart, AR 72160

Abstract

Abstract

Knowledge concerning the seasonal accumulation and partitioning of fertilizer and total N in direct-seeded rice (Oryza sativa L.) is very limited. A field study was conducted on the semidwarf rice cultivar Lemont and a standard-statured rice cultivar Lebonnet to assess N accumulation and partitioning throughout the season. Fertilizer N as 15N-labeled urea was applied at 134 kg N ha−1 either in a single preflood or split applications of 67 kg N ha−1 at preflood and panicle differentiation (PD). A third treatment involved split application of nonlabeled N fertilizer at preflood and 15N fertilizer at PD. Total N and fertilizer 15N uptake as well as the N distribution among leaf blades, leaf sheaths, stems, and panicles were measured biweekly prior to heading and weekly after heading until maturity. Cultivar differences in N uptake and distribution among plant parts were minor. In general, the leaves contained 70% of the plant N at flooding and 60% just prior to heading. The percentage of plant N in the stems and sheaths showed a steady increase from flooding to heading. Soon after heading, the panicle became the plant part with the largest N accumulation and steadily increased in N at the expense of other plant parts. By maturity, the panicle contained two-thirds of the total plant N. Translocation of fertilizer N to the panicle was slower when all of the N was applied preflood, compared with split applications. Maximum fertilizer 15N uptake occurred by 55 d after emergence when all of the N was applied preflood (79% of applied N), and by 69 d after emergence when N was applied in split applications (72% of applied N). Plant samples taken at maturity underestimated fertilizer 15N recovery by 14 to 25%, compared with fertilizer 15N recovery measured by sampling plants 2 to 4 wk before heading.

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