Evaluation of quantity‐intensity relationships of potassium in deeply weathered soil profile developed over granite from peninsular Malaysia

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Abstract
The potassium (K) supplying capacity of a deeply weathered profile developed over granite from Peninsular Malaysia was investigated by employing the quantity‐intensity (Q/I) approach. The values of potential buffering capacity (PBCK), labile K (KL), specific K (KO), and specific K sites (KX) were considerably higher in the saprolite zones as compared to the solum layers. This indicated that depletion of K on cropping would be faster in the solum materials than in the saprolites. Potassium equilibrium activity ratio was in the sequence: solum > middle saprolite > upper saprolite. Free energy values showed low, but sufficient, level of available K reserve in this profile. The relationships of Q/I parameters with physico‐chemical characteristics and clay mineralogy of the profile were discussed. The changes in the Q/I parameters as a function of depth were found to be associated with the contents of clay and organic matter in the solum, while in the saprolites, the clay mineralogy which composed mainly of K‐feldspar, mica, and mica‐smectite seemed to be the main factor.