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This article in SSSAJ

  1. Vol. 44 No. 3, p. 500-505
    Received: June 1, 1979
    Accepted: Jan 8, 1980

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Effects of Lime, Silicate, and Phosphorus Applications to an Oxisol on Phosphorus Sorption and Ion Retention1

  1. T. Jot Smyth and
  2. Pedro A. Sanchez2



Greenhouse and laboratory experiments conducted with a clayey kaolinitic isohyperthermic Typic Haplustox from the Cerrado region of Brazil showed that CaCO3, CaSiO3, and previous P applications decreased P fixation and improved cation retention properties. The amendments were added at rates to replace 1 or 2× exchangeable Al, and P was applied at rates to provide equilibrium solution concentrations of 0, 0.05, 0.1, and 0.2 ppm P. Six months after application, CaCO3 and CaSiO3 at 1× exchangeable Al decreased the amount of previous P sorbed to provide 0.1 ppm P in solution by 18 and 24%, respectively. Previous P applications were more effective in decreasing P sorption than the amendments. A 540 ppm P rate decreased P sorption by 65% without amendments. The combination of amendments + 540 ppm P decreased P sorption by 85 to 91%. Fertilizer P recommendations based on soil solution levels for limed soils should be obtained with soil samples which have also been limed; otherwise the P requirement may be overestimated.

Net negative soil charges increased by 11 to 47% with amendment applications and by 34% with 540 ppm P. The highest P and amendment rates doubled the net negative charge of this soil. Joint applications of P and soil amendments increased the negative charge and decreased the positive charge to a greater extent than when applied separately. Applications of both P and amendments made a major improvement in cation retention against leaching, but may increase anion leaching. P applications significantly increased soil pH and negative ΔpH values.

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