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Soil Science Society of America Journal Abstract -

Differentiation of Soil Nitrogen Fractions Using a Kinetic Approach1


This article in SSSAJ

  1. Vol. 51 No. 2, p. 314-317

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  1. T. H. Carski and
  2. D. L. Sparks2



The chemically induced release of NH4-N from four Delaware soils was monitored over time. The extractants used were 0.02 M KMnO4-0.5 M H2SO4 at 297 K and 0.01 M CaCl2 at 368 K. Data were analyzed using first-order kinetics. The kinetic approach presented does allow direct differentiation of two NH+4 releasing reactions. Two simultaneous first-order reactions were needed to describe three of the soils, while a single equation described the remaining soil. The equations were considered to represent the release of NH+4 from an inorganic and an organic source. Using this approach, estimates of these pools were made and compared with estimates based on traditional batch techniques. Extraction with acid-KMnO4 yielded kinetic estimates of the inorganic and organic pools, which exceeded the batch estimates of these pools. Kinetic estimates based on extraction with CaCl2 were similar to batch estimates of inorganic N, but much less than either acid-KMnO4 or batch estimates of organic N. Neither extractant gives direct evidence for the existence of a chemically active organic pool; however, there is indirect evidence for such a pool.

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