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This article in JEQ

  1. Vol. 22 No. 3, p. 578-583
    Received: Aug 13, 1990

    * Corresponding author(s):
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Relationship between Soluble and Extractable Phosphorus in Some Calcareous Soils of Iran

  1. Seifollah Amin Sichani *,
  2. Shahrokh Zand Parsa and
  3. D.W. Nelson
  1. Agricultural Research Div., Univ. of Nebraska, Lincoln, NE, 68583-0704.



The relationship between water-extractable P (soluble P) and NaHCO3-extractable P was determined in different water/soil ratios. The values of 0, 45, 90, and 180 mg kg−1 soil as KH2PO4 were added to seven calcareous soil series from southern Iran (for two soil series additional P rates of 360, 720, and 1080 mg P kg−1 soil as KH2PO4 also was employed). Soluble P in water/soil ratios of 10:1, 25:1, 100:1, and 500:1 was measured by Murphy and Riley method (1962) after 2 h shaking. Sodium bicarbonate—extractable P also was determined in all soils. The results indicate that there was a linear relationship between the logarithm of soluble and NaHCO3-extractable P when NaHCO3-extractable P was less than 150 mg P kg−1 soil. There also was a linear relationship between soluble P and the water/soil ratio up to 100:1 for these soils. The amount of P released per unit soil weight at water/soil ratios greater than 100:1 was approximately constant.

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