不同肥力条件下黑土及其有机无机复合体的腐殖质组成

采用Kumada法研究了不同肥力黑土及其复合体的腐殖质组成.结果表明,黑土培肥后,粉粒和细砂复合体含量增多;土壤及各级复合体游离态和结合态腐殖质含量得到不同程度提高,但游离态腐殖质的腐殖化度降低.这种作用在粉粒和细砂复合体中表现得更为明显.随复合体粒径增大,复合体有机碳含量、腐殖质提取率、游离态腐殖质含量及游离态胡敏酸的腐殖化度等均有降低趋势.胡敏酸分类结果表明,高肥土壤游离态胡敏酸均为R_p型,低肥则为R_p型和B型.随复合体粒径增大,游离态胡敏酸类型变化序列主要为:A型(粘粒)→B型(粉粒)→R_p型(细砂);无论粒径大小,结合态胡敏酸大多为A型.土壤培肥后,可使全土及各级复合体的游离态腐殖质的腐殖化度降低,进而会发生型变.在黑土中,游离态胡敏酸的型变主要体现在粉粒复合体中,结合态胡敏酸的型变主要体现在细砂复合体中.

Humus composition of black soil and its organo-mineral complexes under different fertility level

Determinations by Kumada method showed that with the improvement of black soil fertility, the free and combined humus contents in soil and its different size organo-mineral complexes increased, but the humification degree of free humus decreased, which was more obvious in silt and fine sand size complexes. The organic carbon content in complexes, humus extraction rate, free humus content, and humification degree of free humic acid decreased with the increasing particle size of complexes. All free humic acids in fertile soil were Rp type, while in unfertile soil, they were Rp and B type. With the increasing particle size of complexes, the type of free humic acids changed in the sequence A type (clay)-->B type (silt)-->Rp type (fine sand). Combined form humic acid mainly belonged to A type, no matter what particle size the complex was. The improvement of soil fertility could make the humification degree of free humus in soil and its complexes decrease, and furthermore, result in type change. In black soil, the type change of free humic acid mainly occurred in silt size complex, and that of combined form humic acid mainly occurred in fine sand size complex.