Increases in the Cation Exchange Capacity of Variable Charge Soils Following Superphosphate Applications1
- G. P. Gillman and
- R. L. Fox2
The cation exchange capacity (CEC) of soils from field plots which were fertilized with concentrated superphosphate for 8 years has been measured. The superphosphate was added in amounts equivalent to those needed to raise solution P to 0.001 to 1.6 µg/ml in the adsorption isotherm. Three variable charge soils from Hawaii, a Hydrandept, a Gibbsihumox, and a Eutrostox were examined, using a new method for estimating the CEC of variable charge soils. This method takes account of pH and ionic strength conditions in the field. Agronomically significant increases in CEC of the surface horizons with increasing superphosphate application were obtained. As a result, the leaching of applied nutrients, Ca, Mg, and K, was retarded, and greater quantities of these cations were present in the 0–50 cm profile than in the plots receiving no P, despite the fact that more cations were removed from the P treated plots by crops grown in succession.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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