(一)土壤腐殖质在土壤形成及土壤肥力上的作用,已为许多研究者所阐明。关于土壤腐殖质本性的问题,现在亦有比较一致的认识,即它们是一类特殊的高分子化合物;不同土类中的胡敏酸,具有特征相同的基本构造骨架,即它们都有环状碳多聚物骨架和链状碳多聚物侧链,同时都含有氮素。但是链的长短和性质以及分子结构缩合的程度则各类土壤 (A) The role of soil humus in soil formation and soil fertility has been elucidated by many researchers. There is now a relatively common understanding about the nature of humus in soil that they are a kind of special macromolecular compounds. The humic acids in different soils have the same basic structural skeleton, that is, they all have cyclic carbon Polymer backbone and chain carbon polymer side chains, all containing nitrogen. But the extent and nature of the chains and the extent to which molecular structures are condensed are all kinds of soils