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This article in SSSAJ

  1. Vol. 52 No. 1, p. 160-165
    Received: Apr 13, 1987

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Phosphorus Supply Characteristics of 33 Soils as Influenced by Seven Rates of Phosphorus Addition

  1. John L. Kovar and
  2. Stanley A. Barber 
  1. Dep. of Agronomy, Purdue Univ., West Lafayette, IN 47907



Soil P supply to plant roots increases after addition of P fertilizer due to both the increase in soil solution P (Pl) and adsorbed P (Ps) that equilibrates rapidly with Pl. Little information is available on the effect of added P on the concurrent increase in Pl and Ps. The objective of this research was to investigate the relation between P added and increase in Pl and Ps of 33 soils. Surface soils collected from the U. S. and Canada were equilibrated moist for three weeks with seven rates of P ranging from 0 to 655 mg P kg−1. High rates of application occur where P is placed in a small fraction of the soil. Values for Pl were obtained from P analysis of displaced soil solution and values for Ps from a 24-h extraction with anion exchange resin. For all soils relation of Pl, curvilinear with P addition, x, was described by Pl = axc + d. Values for c, the curvilinearity, varied from 1.03 to 3.15. There was a negative correlation between c and exchangeable Ca (r = −0.65*, significant at the 0.05 probability level) and soil solution P concentration before P addition, Pli, (r = −0.61*). Adsorbed P increased linearly with P addition for all soils, the slope of the relation varying from 0.35 to 0.86. The slope indicates the fraction of added P extracted with the anion-exchange resin. There was a positive correlation between the slopes and the effective diffusion coefficients, De, for P in the soils (r = 0.47*). There was no significant correlation between c and the adsorption line slope. Development of methods for predicting the effect of added P on Pl and Ps will be useful in quantifying their increase in soil resulting from P addition.

This research was supported in part by a grant from the Fluid Fertilizer Foundation and BARD, United States-Israel Binational Agricultural Research and Development Fund. Contribution of Purdue Univ. Agric. Exp. Stn. Purdue Journal Paper no. 11 114.

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