The Effect of Temperature and Moisture on Exchangeable Potassium

Abstract

Abstract The influence of temperature and moisture on the release of nonexchangeable K to the exchangeable form was studied in the laboratory. Varying moisture from 60 to 100% of moisture equivalent was found to have no effect on the release of nonexchangeable K at temperatures from 1° to 80° C. Temperature caused increases in the level of exchangeable K in all but one case. The higher the temperature, the greater was the rate of release of nonexchangeable K. The first release of K appeared to conform to a first‐order reaction, while subsequent release was of a zero‐order nature. Activation energies were determined from data obtained by the incubation of soils at three temperatures. These values were in the range of 11,000 to 26,000 cal. per mole. Data obtained by oven‐drying soils before and after incubation at 118° C. indicate that the increases in exchangeable K obtained by these two methods were due to different reactions.