Comparison of Partially Acidulated Rock Phosphate and Concentrated Superphosphate as Sources of Phosphorus for Corn
1971
Lutz, J. A.
The data available measuring the relative efficiencies of acidulated rock phosphate at various levels of applied P are limited, and further investigation of this subject is warranted. Florida rock phosphate was acidulated with H₃PO₄ at 20 and 100% of that required to convert rock phosphate to concentrated superphosphate. These two materials plus a check (0 P) were applied as treatments for corn (Zea mays L.) during three consecutive years on an acid soil in field experiments. Rates of total P from each source were 0, 10, 20, 30, and 100 kg/ha, which was broadcast and disked in each year just prior to planting. There was an excellent response to P fertilization. Corn yields were similar from both sources of P at some rates of applied P, while at other rates, P from concentrated superphosphate appeared to be the superior source. Phosphorus content of the ear leaves was not affected by P source in 1968, but differences were evident in 1969 and 1970. Leaf K content in 1970 was significantly increased by the highest rate of applied P from both P sources. There was an increase in available soil P only at the highest rates of applied P. At low rates of applied P, CSP was the most economical source of P. At the highest rate of P application, the 20% acidulated rock phosphate appeared to be more economical
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