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对蔬菜保护土地壤的固钾特征进行了研究，结果表明土壤的固钾率随着土壤速效钾含量的提高和钾素施入量的增加逐渐降低．土壤用于保护地蔬菜栽培以后，速效钾含量明显提高，同时土壤对钾素固定率也随之降低．铵离子可以替代钾离子而被土壤粘土矿物固定，铵离子和钾离子等浓度存在时土壤的固钾率仅是钾离子单独存在时的二分之一，当这两种离子的浓度分别达到300．0μg·g-1时，施入土壤中钾素的固定率降低到50％以下，最低的只有27．7％。因此，在蔬菜保护地条件下，为避免钾素的淋失和土壤溶液浓度的提高，应提倡钾肥与铵态氮化肥分施和钾肥分次施用。
The characteristics of potassium fixation in vegetable soils were studied. The results showed that the rate of potassium fixation decreased with the increase of available potassium and the increase of potassium in soil. After the soil was used for the cultivation of protective vegetables, the content of available potassium increased obviously, meanwhile the fixation rate of soil potassium decreased. Ammonium ions can be replaced by potassium ions and soil clay minerals fixed, the concentration of ammonium ions and potassium ions in the soil when the potassium rate is only potassium ions alone when the half, when the concentration of the two ions reached 300 .0μg · g-1, the rate of fixation of potassium in soil decreased to below 50%, the lowest was only 27.7%. Therefore, under the condition of vegetable reserves, in order to avoid the leaching of potassium and the increase of soil solution concentration, potassium and ammonium nitrogen fertilizers and potassium fertilizers should be advocated.