Thermodynamics and potassium exchange in soils and clay-minerals

This chapter reviews stimulating research on potassium exchange in soil and clay minerals. The essential elements of a thermodynamic analysis of cation-exchange equilibria are presented and their application to potassium exchange in soil and clays are examined. The useful applications have been limited to characterizing the exchange properties of soils and establishing the selectivity of various soils and clays for potassium. No thermodynamic parameter has been found to predict crop yield or response to K+ fertilizer from soil K+ measurements. The use of calorimetrically measured enthalpies of exchange to detect small amounts of impurities in formerly pure clay minerals aids the clay mineralogist. It may also aid agriculturalists, because a more detailed picture of soil mineralogy helps to explain and predict the reaction of a soil when K+ fertilizer is added. One of the most important areas of agricultural research is the modeling of soil-plant processes.

RESP-08843