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Soil Science Society of America Journal Abstract -

Optimizing Phosphorus Fertilization Rates for Soybeans Grown on Oxisols and Associated Entisols1


This article in SSSAJ

  1. Vol. 49 No. 6, p. 1457-1460
    Received: Mar 29, 1985
    Accepted: June 27, 1985

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  1. I. D. G. Lins,
  2. F. R. Cox and
  3. J. J. Nicholaides III2



Although soils vary considerably in their P sorption characteristics, this factor is often not considered in a soil test interpretation. One soil property closely related to P sorption is clay content. Residual P studies were conducted for 4 yr on three tropical soils of similar clay mineralogy, two Oxisols of 63 and 27% clay, and a Quartzipsamment of 12% clay. The Mehlich 1 (1:10) extractable P level was described as a function of time, initial soil P level, and P fertilization rate. One crop of soybeans [Glycine max (L.) Merr.] was grown each year and the yield related to extractable P, which, in turn, was related to the initial P soil level and P fertilization rate for a period of 1 yr. Based on a soybean price of $0.23/kg and a fertilizer P price of $1.23/kg, rates of P were calculated for each of the three soils that would maximize net returns for various initial levels of extractable P. As these rates differed markedly with clay content, a soil test interpretation was created by multiple regression based upon both Mehlich 1 extractable P concentration and clay percentage to predict a recommended rate of fertilizer phosphorus (R) as follows: R = 80 − 2.57(soil P) + 0.01386(clay)2 − 0.003281(soil P)(clay2). This function should be applicable to many soils with similar clay characteristics.

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