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This article in SSSAJ

  1. Vol. 64 No. 1, p. 208-215
     
    Received: Jan 25, 1999
    Published: Jan, 2000


    * Corresponding author(s): kaspar@nstl.gov
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doi:10.2136/sssaj2000.641208x

Oat and Rye Root Decomposition Effects on Nitrogen Mineralization

  1. R. N. Malpassia,
  2. T. C. Kaspar *b,
  3. T. B. Parkinb,
  4. C. A. Cambardellab and
  5. N. A. Nubelb
  1. a Plant Morphology, Universidad Nacional de Rio Cuarto, 5800 Rio Cuarto, Cordoba, Argentina
    b USDA-ARS, National Soil Tilth Lab., 2150 Pammel Dr., Ames, IA 50011 USA

Abstract

Decomposition and mineralization of cover crop roots needs to be understood to determine if N taken up by cover crops is mineralized during main crop growth. Two experiments were conducted in a controlled environment to measure decomposition of oat (Avena sativa L. `Ogle') and rye (Secale cereale L. `Rymin') root residues and to examine its effect on soil N mineralization. In the first, oat and rye roots were mixed with soil and in the second, roots were grown in situ. At 7, 14, 28, 56, 84, and 112 d after the start of decomposition, denitrification, soil NO 3, and soil NH+ 4 were measured to determine net mineralized N. Soil respiration and C and N contained in roots and coarse soil organic matter were measured to determine decomposition. All treatments in both experiments showed an increase in net mineralized N during the first 56 d. After 56 d, net mineralized N in the control remained relatively constant, whereas mineral N continued to accumulate in the treatments with root residues. Net N mineralization of the rye and oat root treatments did not differ. Roots mixed with soil had high respiration rates during the first 3 d and there were no differences between oat and rye root treatments. In the roots in situ experiment, however, respiration peaked for oat roots at Day 12 and for rye roots at Day 33. The oat treatment also had less C and N remaining in roots and coarse organic matter throughout the experiment. Even though oat roots decomposed faster than the rye roots, we predict that <55% of the N contained in the roots of a spring-killed oat or rye cover crop will become available to the following crop.

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