The effect of lime, KCl and parent material on the cation exchange capacity of some acid subsoils of the western Cape

摘要

Cation exchange capacity (CEC) values obtained by22Na dilution for a numberofmineralogically diverse acid subsoils reflected positive responses to lime and to treatment with KCl such that: CEC (unlimed, no KCl) (unlimed + KCl) (limed, no KCl) (limed + KCl). Mean CEC values for the kaolinitic granite soils and for the 2:1 mineral-containing Bokkeveld shale (BS) soils were similar. This similarity masked a wider variability in the CEC values observed for the BS than for the granite soils, particularly in terms of response to lime. The Table Mountain sandstone (TMS) soils had a lower mean CEC but a wider variation between treatments. Overall CEC responses to liming and to applied K respectively, were: TMS BS granite; and: TMS granite BS. CEC values per kg clay#x2212;1increased exponentially with decreasing soil clay content, probably as a function of dilution.