Phosphorus Sorption Characteristics of Bh and Bt Horizons from Sandy Coastal Plain Soils

Abstract

AbstractRetention of land‐applied P is an environmental concern in sandy Coastal Plain regions. Compositional differences between Spodosol Bh and Ultisol Bt horizons are likely to have major consequences for P retention. The purpose of this study was to compare P sorption‐desorption characteristics of Bh and Bt horizons using selective chelation to evaluate the effects of organically complexed Fe and Al in Bh samples. The Bh and Bt samples sorbed comparable amounts of P but Bh samples desorbed a higher proportion of their adsorbed P. After alkaline acetylacetone extraction of metal‐organic complexes, Bh samples lost most of their P adsorption capacity, but their desorption behavior was more like that of samples whose clay fractions were dominated by inorganic metal oxides. Aluminum‐organic matter complexes appear to be responsible for the high P adsorption capacity of Bh horizons as well as for the tendency of these horizons to release P more readily at low solution P concentrations.