An Historical Perspective on the Chemistry and Mineralogy of Soil Potassium.

The chemistry of potassium in soils is controlled by equilibrium and kinetic reactions between the four major forms: solution, exchangeable, nonexchangeable, and mineral. It has often been observed that crops do not respond to applications of potassium. This has been linked to uptake of subsoil K by plant roots and large reserves of nonexchangeable, and particularly,  mineral K that are slowly released to replenish K in solution. Soil tests that are used to assess the need or lack of need for additions of fertilizer K in many cases do not always account for K release from nonexchangeable and mineral K. This can result in unnecessary fertilizer costs, coupled with, lack of increases in crop yield. This presentation will present an historical perspective on soil K chemistry and mineralogy, including assessment of soil tests for K and their relation to crop yields.