Phosphorus Sorption of Subtropical Acid Soils as Influenced by the Nature of the Cation Suite
- J. S. Russell,
- C. S. Andrew and
- E. J. Kamprath
Previous field studies with pasture on subtropical acid soils in eastern Australia showed a long residual effect of relatively low rates of fertilizer P. Samples of six soils from eastern Australia were collected to determine their P sorption characteristics. Monocalcium phosphate solutions containing 0.005 M CaCl2 were equilibrated with samples which were untreated, limed or CaCl2-leached. Measurements were made of the amount of P sorbed and P remaining in solution. The soil chemical properties affecting P sorption, P buffering and amount of P sorbed needed to provide 0.2 µg P mL−1 were determined by multiple regression analysis. Phosphorus sorption and buffer capacity increased with increasing CuCl2-extractable Al and decreased with increasing exchangeable Na saturation or increased soil solution Na. Amounts of sorbed P needed for 0.2 µg P mL−1 in the soil solution were relatively small for the untreated and limed Natrustalfs and ranged from 13 to 37 mg P kg−1 soil. A given application of P fertilizer will provide a higher soil solution P in subtropical soils which contain appreciable Na, such as Natrustalfs, than those in which Ca is the dominant cation.
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