Potassium, one of three main nutrient elements necessitated for plants, is usually divided into fast available
Potassium, slowly available potassium and invalid potassium according to its availability for crops in
soils. The three type of potassium lay in a mobile equilibrium in soils, which can be affected by potassium
fixation and release, thus exerts impact upon the availability of potassium. The soils, rich in 2∶1
clay minerals which have great mounts of specifically adsorptive sites, are not only abundant with reserves of slowly available potassium and high with potential of potassium supplying ability, but also show higher potassium fixation capacity. To a certain extent, this kind of fixation could alleviate potassium from being leached in sandy soils, preserve the fertility and enhance the
fertilizer efficiency. Large parts of available potassium input in the
Soil, however, will turn into non exchangeable K in most other kinds of soils as a result of the fixation, thus only can a little of applied K fertilizer be utilized by current crops. The potassium fixation in soil has become a main impediment factor in increasing the efficiency of K fertilizer under the condition of modern intensive agriculture. The conceptions of the three type of potassium and the processes of potassium fixation and release in soils are expatiated respectively in this paper. The mechanism of potassium fixation and release is summarized. The authors put forward that the types and structure of clay minerals are main factors influencing the capability of potassium supplying and that the tri octahedral clay minerals assume the stronger capacity of potassium fixation after comparing the performance of different type of clay materials. The levels of NH + 4 and phosphor, the status of soil water, as well as the contents of organic matter and hydroxy aluminum, lay important influence upon the fixation and release of potassium in soil. The status and progress in the field of potassium fixation and release are also reviewed.
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