Equilibrium distribution of an ion between soil solution and solid phase was described by a distribution coefficient , k . the k was a ratio of cs and c1 and a conditional equilibrium constant , which cs and c were quantity of k in solid and solution phase respectively 隨水吸力增大,固相鉀離子( cs )比率下降,液相鉀離子比率逐漸增加,分配系數k減小。在水吸力約為1 . 5 10 ~ 5pa時,四種土壤鉀離子在固液相間的分配達到穩定,分配系數為最小。