Abstract: By using X-ray diffraction and laboratory simulation, this paper studied the effects of long-term potassium (K) fertilization on K fixation in black soil, loess soil, and grey desert soil under different ecological conditions and cropping systems. The results showed that long-term K fertilization had greater effects on the K fixation capacity of soils with lower hydromica content. When the K application rate was 400 to 4 000 mg·kg^-1, the K fixation capacity of black soil and loess soil, whose hydromica contents were low or relatively low, decreased by 75-747 mg·kg^-1 and 16-238 mg·kg^-1, respectively, compared with no K application, while no change was observed in grey desert soil whose hydromica content was high. Long-term K application could affect the changes of soil K-bearing minerals, i. e. , slowing down or holding back the transformation of hydromica into mixed-layered mica-smectite, and consequently, decreased the K fixation capacity of soil. The increase of soil slow-available K content and K⁺ saturation owing to the long-term K application also induced the decrease of the K fixation capacity.

Key words: Grazing resistance, Resistant and tolerant thresholds, Grazing resistant strategies