PHYSICAL, CHEMICAL, AND MINERALOGICAL CHARACTERISTICS OF SOILS FROM VOLCANIC ASH IN NORTHERN IDAHO .2. PHOSPHORUS SORPTION

The magnitude of P sorption was related to the extractable allophane content and quality of concretions. The clay fraction adsorbed more P than the silt fraction. Sorption of P was due mainly to the presence of Al in concretions and the presence of higher amounts of amorphous materials. Iron, Al, Mn and other clay minerals contributed to the sorption capacity of the soils. Detailed roles of these factors in sorption of P by soils, clays, and concentrations are discussed.-from Authors