This paper deals with the effect of application of organic materials on improving soil fertility. Experiments showed that PQ of various kinds of combined humus, in general, dropped in first year and rised back next year after organic materials were applied. The extent and time-keeping far the decrease of humification degree depended on the sorts and amounts of organic materials applied as well as the environment conditions under which the organic materials decomposed. The △logk and E₄/E₆ of various kinds of humid acids increased, while their RF values decreased by application of organic materials. Loosely combined HA varied in a wider range than stably combined HA. materials were not only higher but also The oprical density curves in treatments of organic steeper than those in the check.