Studies on the Dissolution of Major Indian Phosphate Rocks in an Acid Soil

Dissolution of eleven phosphate rocks (eight from India and three from USA) In comparison with triple superphosphate (TSP) was studied in an acid soil under flooded as well as unsaturated conditions over a 10 week period. Dissolution of North Carolina phosphate rock was highest followed by Central Florida rock, and relatively low with Tennessee and all Indian phosphate rocks both under flooded and unsaturated conditions. Among the Indian sources, Durmala phosphate rock resulted in relatively higher levels of Bray l extractable P. Significant linear correlations were obtained between the maximum P concentration (water-soluble and Bray 1 extractable P) in acid soil treated with the phosphate rocks under flooded and unsaturated conditions and the degree of isomorphous substitution of carbonate for phosphate in the apatite structure of the phosphate rocks.