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Agronomy Journal Abstract -

Utilization of Labelled Urea and Ammonium Sulfate by Lowland Rice1


This article in AJ

  1. Vol. 70 No. 3, p. 465-467
    Received: Aug 29, 1977

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  1. K. R. Reddy and
  2. W. H. Patrick Jr.2



Urea and ammonium sulfate are the most common fertilizer N sources used to topdress rice (Oryza saliva L.). The high cost of N fertilizer and the possible environmental impact of excess N make it important to obtain good utilization of the fertilizer applied to the crop. The objective of the present investigation was to compare labelled ammonium sulfate and urea in their effect on yield and N utilization in field microplots on Crowley silt loam (typic albaqualf). Nitrogen was applied as an early season top dressing or as a midseason topdressing and the grain and straw yield and recovery of labelled and native N in the grain straw, and soil were measured.

No significant differences in grain and straw yields were observed for the two sources and two times of N application. Ammonium sulfate and urea did not differ significantly in N utilization by the crop. For both sources the recovery of labelled N in the soil-plant system was highest (34 to 55 kg N/ha) in the plots receiving midseason topdressing as compared to the plots receiving early season topdressing (30 to 38 kg N/ha). More native soil N was taken up by the plants during 1976 as compared to the 1975 season.

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