在既含石灰又含石膏的盐渍土上测定代换性阳离子之所以成为困难,是因为在这类土壤中含有三部分盐类:水溶盐、代换性盐和微溶性盐——石灰及石膏.这三类盐在某种程度上说界限并不是很明显的;它们可以互相变换.因此想要毫不混淆地取出其中任一盐类是比较困难的,特别是利用较简便快速的手续.近年来各国学者对这方面做过很多工作,确也获得不少的成绩,但总未得出一套令人满意的方法.不是不能避免各种盐类的互相干扰;不然就是成本太高,速度太慢,不适于大规模生产(例如强用酒精把可溶盐和石膏洗净等法). Determining surrogate cations on salty soils containing both lime and gypsum is problematic because three soils are present in such soils: water-soluble salts, substitutional salts, and sparingly soluble salt-lime and Gypsum These three types of salt, to a certain extent, are not obvious boundaries; they can change each other, so you want to be able to remove any one of them without confusion is more difficult, especially the use of relatively simple and quick procedures In recent years, scholars from various countries have done a great deal of work in this field and have indeed achieved many successes, but they have not come up with a satisfactory solution. They can not avoid the mutual interference of various salts; otherwise they are too costly , Too slow, not suitable for large-scale production (such as strong alcohol to dissolve salt and gypsum, etc.).