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Soil Science Society of America Journal Abstract -

Nitrogen Management and Nitrification Inhibitor Effects on Nitrogen-15 Urea: II. Nitrogen Leaching and Balance


This article in SSSAJ

  1. Vol. 54 No. 1, p. 122-130
    Received: Apr 17, 1989

    * Corresponding author(s):
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  1. D. T. Walters and
  2. G. L. Malzer 
  1. Dep. of Agronomy, Univ. of Nebraska, Lincoln, Nebraska 68583
    Soil Sci. Dep., Univ. of Minnesota, St. Paul, MN 55108



Nitrification inhibitors (NI) may reduce N leaching losses, and should have the greatest effect on sandy soils where leaching potential is high. This study used 27 lysimeters to evaluate the effect of a NI, nitrapyrin [2-chloro-6(trichloromethyl) pyridine], on soil water percolation (SWP) and N leaching losses from an irrigated sandy loam soil (Typic Hapludoll) planted with corn (Zea mays L.), and monitor the fate of a single application of 15N-enriched urea over a multiyear period. Urea was applied at 90 and 180 kg N ha−1 yr−1 for a 3-yr period, with and without NI, and with and without incorporation. Urea + NI reduced SWP between planting and silking in 2 out of 3 yr when growing degree days (GDD) were high. After silking, SWP was reduced when urea + NI was incorporated and leaching load was high. A twofold increase in N rate resulted in an average of 3.4 times more N leached over 3 yr. The NI influenced time of N loss but not total N loss. Leaching losses of fertilizer-derived N (FDN) were delayed 25 to 50 d when urea + NI were incorporated. The leaching load required to reach the maximum rate of FDN loss was higher with urea + NI. Leaching losses of fertilizer N were three times greater when determined by the difference method than by isotope-ratio analysis. Differing results with these two calculations are attributed to isotope dilution with indigenous soil N as a result of microbial activity. Nitrification inhibitors may reduce the potential for nonpoint-source pollution by delaying NO3 leaching, but will be most effective if coupled with proper N rates and conservative irrigation water management.

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