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This article in SSSAJ

  1. Vol. 53 No. 6, p. 1884-1887
     
    Received: Apr 4, 1989
    Published: Nov, 1989


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doi:10.2136/sssaj1989.03615995005300060045x

Seasonal Uptake Patterns of Fertilizer Nitrogen Applied in Split Applications to Rice

  1. C. E. Wilson ,
  2. B. R. Wells and
  3. 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

When rice (Oryza sativa L.) is grown in a direct-seeded, delayed-flood system as used in the southern USA, split topdress applications of N fertilizer have proven to be one of the most effective methods for achieving relatively high grain yields and efficient fertilizer-N uptake. Knowledge concerning the seasonal uptake patterns of fertilizer N applied in split applications is limited. Consequently, a field study was conducted to measure the seasonal uptake of N fertilizer from split applications made at preflood, 1.3-cm internode elongation (IE), and 14 d after IE (IE + 14 d). To evaluate each fertilizer application, 15N-labeled urea (2.42 atom% 15N) was applied at preflood (10 g N m−2), IE (5 g N m−2), or IE + 14 d (5 g N m−2). Fertilizer N contained in the soil as NH4, NO3, and organic N were determined periodically after each 15N application, along with the fertilizer and total N in the rice roots, shoots, and panicles. Plant uptake of fertilizer N from the preflood application was essentially complete within 21 d after application (63.2% of the applied N). Nitrogen uptake was essentially complete within 3 d after application of the midseason treatments. Three days after IE, 63.3% of the applied N had been taken up by the plant whereas the plant had taken up 70.1% of the applied N 3 d after the IE + 14 d N application. Approximately 20% of the fertilizer N was recovered in the soil organic fraction at maturity regardless of the time of fertilizer application. Fertilizer N incorporated into the soil organic fraction reached a maximum within 21 d after the preflood treatment.

Contribution of the Dep. of Agronomy, Univ. of Arkansas and the Arkansas Agric. Exp. Stn. Supported in part by the Tennessee Valley Authority's National Fertilizer Development Center and the Arkansas Rice Research and Promotion Board.

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