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This article in AJ

  1. Vol. 58 No. 6, p. 621-625
    Received: Apr 2, 1966

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Effect of Partial Acidulation and Elemental Sulfur on Availability of Phosphorus in Rock Phosphate1

  1. D. L. Ashby,
  2. W. E. Fenster and
  3. O. J. Attoe2



A study was made of the effect of partial acidulation of rock phosphate, coating with elemental S, granule size, placement, and soil pH on yield and uptake of P and S by ryegrass grown on Miami (pH 6.7) and Dubuque (pH 6.0 and 7.0) silt loams in the greenhouse. In most cases, both yield and P uptake increased with each increase in level of acidulation; however, the results for the 50 and 100% levels were quite similar. Total P recovery by the ryegrass was highly correlated with the percentage of total P that was available (water soluble plus citrate soluble) in the fertilizer. Mixing of the granules with the soil gave higher yields and P recovery than banding, and the 10- to 20-mesh granules were generally more effective than the 5- to 10-mesh size on the soil at pH 6.0. Coating of the granules with elemental S gave no significant increases in yield but increased P recovery significantly from the 5- to 10-mesh granules in several cases. Both yield and P uptake for rock phosphate were higher at pH 6.0 than 7.0.

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