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This article in AJ

  1. Vol. 76 No. 2, p. 240-242
     
    Received: June 8, 1983


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doi:10.2134/agronj1984.00021962007600020016x

Fate of 15N-Depleted Ammonium Nitrate Applied to No-Tillage and Conventional Tillage Corn1

  1. B. K. Kitur,
  2. M. S. Smith,
  3. R. L. Blevins and
  4. W. W. Frye2

Abstract

Abstract

Crop recovery and soil immobilization of fertilizer N under two different tillage systems was observed in a 3-year study. Corn (Zea mays L.) was fertilized with 84 or 168 kg N ha−1 as 15N-depleted NH4NO3. Nitrogen was surface applied as a solution on a Maury silt loam soil (fine , mixed, mesic Typic Paleudalfs). There was no mechanical disturbance of the soil in the no-tillage treatment (NT); conventional tillage (CT) consisted of spring plowing and disking. Grain yields with NT tended to be lower than yields with CT at the low N rate but equal or greater at the high N rate. However, these differences were not statistically significant. In 1980 fertilizer recovery in grain was 21 vs. 38 kg N ha−1 for NT and CT, respectively, at the low N rate. At the high N rate, N recovery by corn grown under NT and CT was not significantly different. Results were similar in 1981. After adding I5N-depleted fertilizer to the same plots for 3 years, 71 to 75% of the fertilizer was accounted for in harvested grain, stover, or soil. Neither tillage nor N rate had a large effect on the fraction of fertilizer N missing and presumed lost by denitrification and leaching. Nitrogen fertilizer remaining in the NT soil was 42% of that applied at the low fertilizer rate and 39% of that applied at the high N rate. In the CT plots apparent immobilization was 28 and 37% for the low and the high N rate, respectively. Approximately one-half of the N apparently immobilized was located in the surface 5 cm of the NT soil, but immobilized N was more uniformly distributed in the top 30 cm of the CT soil. Increased immobilization of N at the surface of the NT soil seems to be the most likely explanation for reduced crop recovery of fertilizer with NT at low N rates.

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