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Soil Science Society of America Journal Abstract -

Influence of Cropping Intensity and Nitrogen Fertilizer Rates on In Situ Nitrogen Mineralization


This article in SSSAJ

  1. Vol. 63 No. 1, p. 129-134
    Received: Dec 16, 1996

    * Corresponding author(s): rkolberg@sidney.ars.usda.gov
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  1. R. L. Kolberg ,
  2. D. G. Westfall and
  3. G. A. Peterson
  1. USDA-ARS, 1500 N. Central Ave., Sidney, MT 59270
    Dep. of Soil and Crop Sci., Colorado State Univ., Ft. Collins, CO 80523



Cycling of N through an agroecosystem can be managed more effectively if effects of N management and cropping sequence on soil N microbial processes are understood. Effects of cropping intensity and N fertilizer rate on net soil N mineralization were studied as well as their correlation with precipitation, air temperature and soil water content. Net soil N mineralization was measured by incubating undisturbed soil cores (15-cm depth) containing anion and cation exchange resins at their bottoms. Cores were incubated during each of five time periods (3–4 wk each) during the fallow phase (mid-April to mid-September) of two no-till cropping systems, wheat (Triticum aestivum L.)-fallow (WF) and wheat-corn (Zea mays L.)-fallow (WCF). Past N fertilizer applications were over four rates with total amounts applied during the previous 6 yr of 0, 95, 190, and 286 kg N ha-1 in WF and 0, 134, 269, and 403 kg N ha-1 in WCF. Soils were an Aridic Paleustoll at Sterling and an Aridic Argiustoll at Stratton in eastern Colorado. Total net N mineralization in WCF was half that in WF (22 vs. 43 kg N ha-1; 2-site average), probably due to greater immobilization as evidenced by nearly three times greater accumulation of crop residue on the soil surface after 6 yr of no-till management. Greater conservation of applied N and soil N can be expected in the more intensive WCF system. Total mineralized N increased with N rate by = 0.2 kg ha-1 for each kg ha-1 of previously applied N. Precipitation in combination with air temperature and their interaction term gave the best prediction of average daily N mineralization at both sites.

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