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Potassium (K) fixation by seven soils, including black soil, fluvo-aquic soil, grey desert soil, loess soil, paddy soil, red soil and purple soil, was determined by laboratory simulation under a fifteen-year-period of long-term fertilization. Factors affecting soil K fixation were then discussed by factor analysis and stepwise regression. Magnitude of soil K fixation rate was as follows: the black soil > the purple soil > the loess soil > the fluvo-aquic soil > the paddy soil > the grey desert soil > the red soil. Our results showed that soil K fixation capacity was significantly affected by the clay mineral types in the soils. Potassium fixation capacity of soils, whose 2:1 layer silicates were dominant minerals, was af- fected by two components extracted by the method of principal component analysis: the first including soil available K, slow available K and K+ saturation, and the second including cation exchange capacity (CEC), soil organic matter (SOM) and <0.002 mm clay contents. Potassium fixation rate was mainly affected by K+ saturation and CEC with lower added K concentration (from 0.4 to 1.6 g/L), and by K+ saturation and <0.002 mm clay content with higher added K concentration (from 2.4 to 4.0 g/L).
Potassium (K) fixation by seven soils, including black soil, fluvo-aquic soil, gray desert soil, loess soil, paddy soil, red soil and purple soil, was determined by laboratory simulation under a fifteen-year-period of long-term Fertilization. Factors affecting soil K fixation were then discussed by factor analysis and stepwise regression. The size of soil K fixation rate was as follows: the black soil> the purple soil> the loess soil> the fluvo-aquic soil> the paddy soil> the gray desert soil> the red soil. Our results showed that soil K fixation capacity was significantly affected by the clay mineral types in the soils. Potassium fixation capacity of soils, whose 2: 1 layer silicates were dominant minerals, was af- fected by two components extracted by the method of principal component analysis: the first including soil available K, slow available K and K + saturation, and the second including cation exchange capacity (CEC), soil organic matter (SOM) and <0.002 mm clay contents. Potassium fixation rate was mostly affected by K + saturation and CEC with lower added K concentration (from 0.4 to 1.6 g / L), and by K + saturation and <0.002 mm clay content with higher added K concentration (from 2.4 to 4.0 g / L) .