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This article in SSSAJ

  1. Vol. 51 No. 6, p. 1460-1465
    Received: Feb 6, 1987

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Kinetics and Mechanisms of Potassium Release from Sandy Middle Atlantic Coastal Plain Soils1

  1. M. C. Sadusky,
  2. D. L. Sparks,
  3. M. R. Noll and
  4. G. J. Hendricks2



Kinetics of K release were investigated on a Kenansville loamy sand (loamy, siliceous, thermic Arenic Hapludults), a Rumford loamy sand (coarse-loamy, siliceous, thermic Typic Hapludults), and a Sassafras fine sandy loam (fine-loamy, mixed, mesic Typic Hapludults) from the Delaware Coastal Plain. Previous field experiments had shown that corn (Zea mays L.) grown on these soils did not respond to K applications. The soils contained high levels of total K ranging from 22.5 to 46.5 cmol kg−1. Most of the total K was in the mineral form, particularly feldspars, and was contained in the sand fractions of the soils. Kinetics of K release from the whole soils and from the coarse, medium, and fine sand fractions were studied using a H-saturated resin and 0.01 M oxalic acid. Potassium release from the whole soils, using the resin, ranged from 0.172 to 0.251 cmol kg−1 over a 30-d period, and significantly more K was released with the resin than with oxalic acid. The K release that occurred from the sand fractions was attributed to the highly weathered nature of the K-feldspars in these soils as observed by electron microbeam analyses. The mechanism of K release from the soil feldspars appears to be a surface-controlled reaction.

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