Phosphorus‐sorption characteristics of intensely weathered soils in south‐central kentucky

Abstract

Studies were conducted to investigate phosphorus (P)‐sorption characteristics of some intensely weathered soils in south‐central Kentucky. Phosphorus adsorption characteristics reflected the chemical and mineralogical properties of the soils studied. All adsorption data were adequately described by first order kinetic reactions which implied that the soils have uniform surfaces for P sorption. In spite of the limitations of the Langmuir equation, its usefulness in summarizing data into one adsorption maximum value was demonstrated by nearly identical adsorption maxima estimated by three linear transformations of the equation and small deviations from the observed maxima. Variations in adsorption maxima between surface and subsoils and among soils were best correlated with extractable aluminum (Al) (r = 0.93, p<0.01) and crystalline iron (Fe) oxy‐hydroxides (r = 0.97, p<0.01). Clay content was also highly correlated with P sorption (r = 0.97, p <0.01) as well as with extractable Al (r = 0.83, p<0.05) and crystalline Fe oxides (r = 0.92, p<0.01) suggesting that its contribution may have been through its association with these soil components. In contrast, organic matter had a negative association with P sorption (r = ‐0.83, p<0.05). The results indicate higher P sorption in subsoil than in surface horizons, controlled mainly by extractable Al and crystalline Fe oxyhydroxides.

Notes

Contribution from the Department of Agronomy, University of Kentucky, Agricultural Experiment Station, Lexington, KY 40506 (Journal Paper No. 93–3–95).