Waste pond phosphate compared with rock phosphate and superphosphate as a fertilizer
1942
Volk, G.W.
A number of greenhouse and field experiments were carried out to determine the relative availability of phosphorus in superphosphate, waste pond, and rock phosphates. Sumter, Eutaw, and Cecil clays; Hartsells very fine sandy loam; Norfolk fine sandy loam; and Decatur clay loam were used in the greenhouse studies. The field experiments were conducted on decatur clay and clay loam, Cecil clay, Hartsells very fine sandy loam, and Norfolk fine sandy loam. The following general conclusions were drawn from these experiments: 1. The results from greenhouse pot tests and field experiments indicate that superphosphate is far superior to waste pond or rock phosphate as a source of phosphorus for the growth of cotton, sorghum, hairy vetch, and Austrian peas. 2. Neither rock nor waste pond phosphate increased the growth of vetch or sorghum significantly on Sumter clay (a calcareous soil), while superphosphate greatly increased the growth of these plants on this soil. 3. Waste pond and rock phosphate appear to be equal in their ability to supply phosphorus for plant growth. 4. As the rate of application of waste pond or rock phosphate was increased from 48 to 384 pounds of P2O5 per acre, there was very little, if any, increase in the crop yields.
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