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Soil Science Society of America Journal Abstract -

Simulation of Nitrogen-15 Immobilization by the Model NCSOIL1


This article in SSSAJ

  1. Vol. 51 No. 1, p. 102-106
    Received: Feb 28, 1986

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  1. Aviva Hadas,
  2. J. A. E. Molina,
  3. Sala Feigenbaum and
  4. C. E. Clapp2



The computer model NCSOIL computes the dynamics of C and N transformations in soil. In its original version, the microbial biomass assimilated organic N from the decay of organic pools, and inorganic N was immobilized only when decomposed organics were deficient in N with respect to biomass needs for growth (NCSOIL—direct version). A new version was presented in which it was assumed that microbial biomass immobilized N only from the inorganic pool, while the decay of organic N always resulted in N mineralization (NCSOIL-MIT version). NCSOIL-MIT was calibrated and tested for the incorporation of inorganic 15N in the organic soil N against experimental data and compared with the direct version. Net N mineralization was highly sensitive to the microbial efficiency of soil decomposable organic C incorporation. An efficiency of 0.2 gave a good account of net N mineralization for soils unamended with organic substances. NCSOIL-MIT simulated the incorporation of 15N, added as NH4, into the organic soil pools. The kinetics of 15N immobilization was sensitive to microbial efficiency as well as to other parameters that control soil N turnover. NCSOIL—direct version required the decomposition of polysaccharide-like material in order to obtain 15N incorporation in the soil organic pools, and the kinetics of 15N immobilization depended on the rate of polysaccharide decomposition.

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