Relative Availability of Phosphorus in Fertilizers Varying in Solubility of the Phosphorus
1965
Wright, Bill C. | Murphy, B. C. | Gilliam, J. W.
Twenty-eight NPK fertilizers varying in solubility of the phosphorus were compared by band application and cropping to corn (Zea mays L.) in the greenhouse. Phosphorus uptake and per cent superphosphate equivalent were determined for each of two crops and for a combination of both crops. The per cent superphosphate equivalent ranged from 14 to 135 in the first crop, from 15 to 98 in the second crop, and from 13 to 111 for the total of both crops. Correlation coefficients for the relationships between superphosphate equivalent and water-soluble and Netherlands alkaline ammonium citrate-“available” P (NAAC-“available” P) were highly significant for crop I, crop II, and the total of both crops. The correlation coefficients relating superphosphate equivalent to AOAC-“available” P were barely significant at the 5% level. It is concluded from these results that both water-soluble and NAAC-“available” P are good criteria to use in judging phosphate fertilizer quality for crops and it is obvious that AOAC-“available” P is poorly related to plant available P.
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