Abstract
A test for phosphate rock (PR) reactivity has been developed based on a representation of certain fundamental properties of the rocks designated the Dissolution Rate Function. The function and properties have been shown to be those important in models of the dissolution rate of PRs in soil. The properties are size or mass distribution with size, solubility product, P content and particle density. In practice the solubility product is measured in terms of the P concentration attained in a standard solution, simulating that in an average soil with respect to pH, Ca and ionic strength.
The test compares favourably with those using citric and formic acids, using published results for the relative agronomic effectiveness of 11 PRs, both unground and ground. The agronomic data also indicated that particle sizes < 0.15 mm can be regarded as equivalent to the size range of 0.10 to 0.15 mm.
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Watkinson, J.H. A test for phosphate rock reactivity in which solubility and size are combined in a dissolution rate function. Fertilizer Research 39, 205–215 (1994). https://doi.org/10.1007/BF00750248
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DOI: https://doi.org/10.1007/BF00750248