Effect of liming and parent material on the potassium quantity/intensity relationships of some upland soils of the western Cape

Abstract

Liming and parent material had major effects on the potassium (K) quantity/intensity (Q/l) relationships of a varied group of naturally base-depleted upland soils of the western Cape. Departures from the usual Q/l curve form were observed, the individual curve sections probably representing specific exchanger states. K buffering (PBC^K) in the limed Bokkeveld shale (BS) soils was 4,0-fold that of the limed granite and 6,5-fold that of the limed Table Mountain sandstone (TMS) soils. The response in terms of PBC^K to liming by the BS soils was 4,7 and 5,1-fold that of the granite and TMS soils respectively. The granite soils were characterized by high levels of K release (ΔK_o), that from the unlimed granite soils being 15,9-fold that from the unlimed BS soils. Relative to the TMS and BS soils, liming had a very limited effect on Δ_o in the granite soils.

Keywords:

• Buffering
• mineralogy
• potassium
• Q/l