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This article in SSSAJ

  1. Vol. 39 No. 3, p. 549-551
    Received: Sept 11, 1974
    Accepted: Nov 5, 1974

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Conventional and Controlled-Release Nitrogen Sources for Rice1

  1. B. R. Wells and
  2. P. A. Shockley2



Tests were conducted for the years 1967–1972 with rice (Oryza sativa L., cv. ‘Starbonnet’) to compare various formulations of sulfur-coated urea (SCU) and iso-butylidene diurea, (I.B.D.U.) with urea and ammonium sulfate as nitrogen sources on both silt loam and clay soils. The N sources were applied either preplant or topdress at rates up to 235 kg/ha to drill-seeded rice which was flooded at approximately 2 weeks following seedling emergence. Grain yields, dry weight, and N uptake indicated that the controlled-release N sources could be used to regulate rate of N supply to the plant throughout the growing season. Growth of direct seeded rice was slowed considerably during the early part of the growing season due to the slow rate of N release but grain yields were not drastically altered. Grain yields on the silt loam soils following use of the controlled-release N fertilizers were consistently equal to those following use of urea or ammonium sulfate. On the clay soils under intermittent flooding, use of SCU resulted in increased yields as compared to urea applied preplant, and in one year resulted in increased yields as compared to urea applied in split top-dress doses. Both SCU and I.B.D.U. were suitable N sources for rice growing under the water management systems employed in these studies.

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