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This article in SSSAJ

  1. Vol. 30 No. 2, p. 248-253
    Received: July 7, 1965
    Accepted: Oct 21, 1965

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Soil Phosphorus in South Dakota: II. Comparisons of Two Availability Tests with Inorganic Phosphorus Fractions Among Soil Series1

  1. F. C. Westin and
  2. G. J. Buntley2



Linear correlations are presented to compare the Bray and Olsen availability tests for soil phosphorus with four inorganic P fractions, clay content, and pH. The soils represent two great soil groups, several general profile textures, several parent materials, and three horizons.

Although trends are indicated when general profile textures, parent materials, and horizons are considered separately, the clearest relationship between the availability tests and the four inorganic P fractions is with great soil group. When all Chernozem samples are considered together the Bray method gives higher positive correlations with the P fractions than the Olsen method. For Chestnut soils considered together the Olsen method gives higher positive correlations than the Bray method. Only one correlation among the Chernozem and Chestnut soils had a significant z value, however. Among the Chernozems when the r values of the textures, parent materials, and horizons are placed within their appropriate great soil group the Bray method has higher r values for 28 of the 31 positive correlations involved. Two of these had significantly higher r values as determined by the z test. When this procedure is followed for the Chestnuts the Olsen method has higher r values for 18 of the 29 positive correlations involved. Eleven of these correlations had significant z values.

Clay content, pH, and Ca-P generally were involved in more negative than positive correlations with the Olsen and Bray methods with the Chernozem and Chestnut soils. The difference in the behavior of the Bray and Olsen reagents between the Chernozem and Chestnut soils used in this study probably is related to climate and its influence on the degree of development of the two great soil groups involved.

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