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This article in SSSAJ

  1. Vol. 75 No. 1, p. 317-323
     
    Received: Mar 15, 2010
    Published: Jan, 2011


    * Corresponding author(s): gilmour@uark.edu
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doi:10.2136/sssaj2010.0123

Nitrogen Mineralization from Soil Organic Matter: A Sequential Model

  1. John T. Gilmour *a and
  2. A. Mauromoustakosb
  1. a P.O. Box 1109, Fayetteville, AR 72702
    b Agricultural Statistics Lab., Univ. of Arkansas, Fayetteville, AR 72701

Abstract

A reliable method to predict N mineralization from soil organic matter (SOM) has proved difficult across a wide range of soils. Previous prediction models used discrete pool(s) of SOM that simultaneously decompose and mineralize organic N according to zero- or first-order kinetics, with each pool characterized for size and N mineralization rate. We propose a different approach: two N pools based on total N that decompose and mineralize organic N in sequence according to first-order kinetics. Data sets from four long-term studies were used to evaluate the sequential model. The 108 soils represented differing soil depths, tillage practices, organic amendments, and cropping systems. The rate constant for Pool I was correlated with N mineralization during the first week (k 1wk), calculated using long-term data. The percentage of total N in Pool I was estimated using the rate constant for Pool I. The rate constant for Pool II was related to the Pool I rate constant and the percentage of total N in Pool I. Because a long-term mineralization study to determine k 1wk is impractical as a routine test, k1wk was correlated with total N, CO2 evolution at 3 d, and clay content using data from one study (38 soils). The rate constant and size of Pool I and were also correlated with total N, CO2 evolution at 3 d, and clay content. An equation describing the impact of temperature and water holding capacity on the rate constant for Pool I suggested that a single Q 10 value is inappropriate for N mineralization from SOM.

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