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Soil Science Society of America Journal Abstract -

Root-Zone Mineral Nitrogen Changes as Affected by Crop Sequence and Tillage


This article in SSSAJ

  1. Vol. 58 No. 5, p. 1464-1469
    Received: Sept 1, 1993

    * Corresponding author(s):
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  1. B. D. Meek ,
  2. D. L. Carter,
  3. D. T. Westermann and
  4. R. E. Peckenpaugh
  1. USDA-ARS, Soil and Water Management Research Unit, 3793 N 3600 E, Kimberly, ID 83341



Crop sequence and tillage affect soil mineral N (NH4 plus NO3) and NO3 leaching below the root zone following alfalfa (Medicago sativa L.). A 2-yr field experiment was conducted in south-central Idaho to determine the effect on soil NO3 levels of a corn (Zea mays L.)-wheat (Triticum aestivum L.) rotation compared with a bean (Phaseolus vulgaris L.)-bean rotation and to demonstrate improved N utilization with a corn-wheat rotation. Alfalfa, growing on an irrigated Portneuf silt loam (coarse-silty, mixed, mesic Durixerollic Calciorthid), was killed in October 1989 with herbicide. Treatments were: (i) BT-BT: conventional tilled bean grown in 1990 and 1991; (ii) CNT-WNT: no-till silage corn grown in 1990, and no-till winter wheat grown in 1990–1991; and (iii) CT-WT: same as CNT-WNT but under conventional tillage. Similar amounts of soil N were mineralized the first (275 kg N ha−1) and second (213 kg N ha−1) year after killing the alfalfa in all treatments. The BT-BT treatment had the highest growing-season soil mineral N (up to 251 kg ha−1, 0–0.45-m depth) because the N uptake by bean was lower (187 kg N ha−1) than corn (252 kg N ha−1, average of CT-WT and CNT-WNT treatments) in 1990 and later than winter wheat uptake in 1991. Most wheat N uptake had occurred by late June when bean uptake was just starting. A rotation that follows alfalfa with corn or a crop with a similar N uptake pattern, instead of bean, will save N fertilizer, lower soil NO3 levels, and reduce NO3 leaching potential.

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