Effect of Extractant and Selected Soil Properties on Predicting the Correct Phosphorus Fertilization of Soybean
1989
Lins, I. D. G. | Cox, F. R.
The rate of phosphorus required to maximize soybean [Glycine max (L.) Merr.] yields is dependent on the concentration of extractable P along with other chemical and mineralogical characteristics of the soil. Clay content, surface area, P adsorption maximum, type of clay, and extractable phosphorus were evaluated in order to enhance the prediction of the rate of P required for optimum soybean growth on seven acid soils in the greenhouse. The soil test extractants were: Mehlich-1, Mehlich-3, Bray-1, and an ion exchange resin method. The critical P level by each extraction method was correlated with clay content and, in one case, also with type of clay. Clay content and surface area were the most effective additional criteria found to improve the prediction of P fertilizer rate. The Mehlich-3 extractant was superior to Bray-1 and the resin method; Mehlich-1 was least predictive. From a practical standpoint, clay content and extractable P offer the best means of predicting the rate of P required.
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