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This article in AJ

  1. Vol. 97 No. 4, p. 1037-1045
     
    Received: Sept 2, 2003
    Published: July, 2005


    * Corresponding author(s): bstevens@sidney.ars.usda.gov
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doi:10.2134/agronj2003.0212

Fate of Nitrogen-15 in a Long-Term Nitrogen Rate Study

  1. W. B. Stevens *a,
  2. R. G. Hoeftb and
  3. R. L. Mulvaneyc
  1. a Northern Plains Agric. Res. Lab., 1500 N. Central Ave., Sidney, MT 59270
    b Dep. of Crop Sci., 1102 S. Goodwin Ave., Univ. of Illinois, Urbana, IL 61801
    c Dep. of Nat. Resour. and Environ. Sci., 1102 S. Goodwin Ave., Univ. of Illinois, Urbana, IL 61801

Abstract

A better understanding of how N management practices affect transformations and movement of fertilizer N may lead to more efficient N management. The objectives of this work were to determine how long-term N fertilizer history in a continuous corn (Zea mays L.) production system affects (i) movement of fertilizer N through the soil profile and (ii) cycling of fertilizer N between available and nonavailable soil forms. Nitrogen-15-labeled ammonium nitrate (15NH4 15NO3) was applied at 0, 67, 134, 201, or 268 kg N ha−1 to subplots of long-term N rate plots. Twenty to 55% of labeled N was converted into either organic or clay-fixed forms during the first growing season, with the percentage decreasing with increasing N application rate. Significantly more N was released from nonavailable forms in plots where the historical N application rate had exceeded the long-term optimum (186 kg ha−1) than in plots that received lower rates. Little fertilizer-derived N leached from the profile during the first growing season, but losses did occur during the off-season and subsequent growing season when N application rate was higher than the optimum. It was concluded that a history of excessive N application may decrease response of subsequent crops to fertilizer N due to greater release from nonavailable N forms, most likely as a result of increased mineralization of crop residues and recently formed soil organic N.

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