A Study on the Composition Characters of Combined Humus in Cultivated Soils of Jilin Province

By means of a chemical method, the composition characters of combined humus of cultivated soils in Jilin province were studied. The results showed that in three types of soils tested, 72%～95% of the organic matter was combined humus; the relative contents of combined humus were different in different types of soils, highest in Phaeozem and lowest in Chernozem; and combined humus in different types of soils all existed in a chiefly loose state. The relative content and HA/FA of combined humus of down layer soil (20～40 cm) were all higher than those of up layer soil (0～20 cm) in Ablic, Phaeozem and Chernozem. The relative contents of combined humus all changed in regularity with the increase of soil grain size. Under this condition, relative contents in Ablic increased, but in Phaeozem and Chernozem they decreased. The total relative contents of combined humus in Ablic, Phaeozem and Chernozem increased with the increase of fertility level. Under this condition, relative contents of three combined humus in Phaeozem all changed in regularity. The loosely combined humus and the tight combined humus increased with the increase of fertility level, but the stably combined humus took on the opposite changing state. The relative content of tight combined humus in Chernozem only decreased with the increase of fertility level while HA/FA all increased with the increase of fertility level.