Field and laboratory experiments were conducted to characterize the evolution characteristic of potassium (K) and its mechanism as affected by different climates, cropping systems, and long-term fertilization, and to investigate the effect of long-term fertilization on K fixation capacity using laboratory simulating methods and X-ray diffraction, and the nonexchangeable K release in 0.

The better extracting method and kinetic model for describing the release and rate of soil non exchangeable K were discussed with Elovich, Second order kinetic models by 0 50 mol· L -1 HNO 3, 0 01 mol·L -1 oxalic acid and H resin successive extraction under constant temperature and pot exhaustion of ryegrass.

The kinectics characteristics of the nonexchangeable potassium release from the soil in Shaanxi is investigated with the Hsaturated resin absorbing method.