Charge Characteristics of Soils as Affected by Phosphate Sorption

Abstract

AbstractThe increase in cation exchange capacity (CEC) of six Connecticut soils varied from 11 to 88% on phosphate sorption from dilute solutions. As the phosphate sorbed increased, the exchange capacity also increased. The amount of P required to produce an increase of 1 meq in CEC varied with pH; at pH 5, 80 mg P was required for an increase of 1 meq in CEC while at pH 7.5, only 40 mg P was required for the same increase. The increase in CEC at pH 5 is attributed primarily to the replacement of octahedrally coordinated water molecules on sesquioxide surfaces while at higher pH values, replacement of hydroxyl ions by phosphate ions becomes more important.