KINETICS OF POTASSIUM ADSORPTION IN SELECTED SOILS FROM NORTHERN CHINA

The kinetics of potassium adsorption was studied, by using a self?developed continuous flow apparatus, for 25 soil samples from 12 soil types of northern China. The adsorption rate to applied potassium was highest in the beginning, and accumulative amount of potassium adsorbed increased rapidly. It became lower and lower as this process proceeded,and soil was completely saturated by potassium after a certain time. This adsorption process can be well simulated by one first order reaction. The adsorption parameters varied a lot among different soils. The period of adsorption lasted, total amount of potassium adsorbed,maximum and average rates of potassium adsorption ranged from 150 to 720min, 138.7～2549.6 mgkg-1 , 6.5～17.4 mgkg-1min-1 and 0.92～3.54 mgkg-1min-1,respectively.All these adsorption parameters are closely correlated with soil clay content,organic matter content and cation exchange capacity. There was a clear tendency that,by moving from west to east in terms of the location of the soil samples,the K adsorption power of the soils gradually increased.