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Abstract

 

This article in SSSAJ

  1. Vol. 35 No. 5, p. 718-721
     
    Received: Jan 26, 1971


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doi:10.2136/sssaj1971.03615995003500050026x

Interpretation of Curves Describing Soil Potassium Exchange1

  1. S. J. Smith,
  2. M. Liu,
  3. L. J. Clark and
  4. A. D. Scott2

Abstract

Abstract

Curves describing the release of K from soil samples in NaTPB solutions depict a linear relationship between the amount of K replaced and the logarithm of the extraction period. Such curves are quite different from the diffusion-controlled curves observed with mica particles and have yet to be explained. Reports of a similar relationship being observed with soil organic N release that also obeyed a second-order reaction led to an unsuccessful application of second-order kinetics to the release of K from 16 soils. On the other hand, linear K-releases versus log t curves were obtained by combining K-release curves for mica particles of different size and by placing mixtures of mica particles in the same NaTPB solution. Therefore, a soil was fractionated, and the K-release curves for the individual size-fractions were determined. The curves for the soil fractions were nonlinear and more like mica curves, whereas various combinations of these curves yielded linear K-release versus log t relationships like those observed with soils. Thus, the curves for soil K-release merely represent the combined effects of various particle sizes in the soil and not a distinctive mode of release.

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