STUDY ON THE REGULAR INCREASE AND DECLINE OF ORGANIC MATTER IN SALT-AFFECTED SOILS OF HUANGHUAIHAI PLAIN

A 7-year miniplot experiment showed that under a cropping system with two harvests in one year and on salt-affected in land soils, the equilibrium content of their organic matter was about 1. 5% in the monsoon climatic region of Huang-huaihai Plain. But the length of time, within which soil organic matter content reached equilibrium, and the rate of accumulation of soil organic matter were different owing to different measures adopted in the same conditions of climate, basal soil fertility and soil texture. The soil organic matter accumulated more rapidly with higher C /N ratio organic manures which contained more lignin. Before its attending to the equilibrium the soil organic matter was linearly correlated with the quantity of organic manures applied.Therefor. in order to meet the requirements of high-stable crop yield in Huang-huaihaiPlain and to control the salt accumulation in the soil surface, the efficoient measures for rapid increase in the organic matter are to lncorporate crop straw into the soil, to apply dung-manure or plant winter -grazing crops in the cotton fields to develop the animal husbandry and to increase the amount of good quality manure.