Method for preparation of coated release-controlled compound fertilizer

The preparation process of coated release-controlling composite fertilizer includes the preparation of coating liquid and the coating of composite fertilizer grain. In common pelletizing apparatus and under specific technological condition, granular composite fertilizer is coated with coating layer with PVA as degradable polymer soil improving agent, natural starch and fertilizer effect prolonging agent as main components to form the coated release-controlling composite fertilizer. The coated release-controlling composite fertilizer has simultaneously controlled releasing nitrogen, phosphate and potash components, degradable coating, and fertilizer effect period as long as 70-90 days. It has high fertilizer utilization and less loss.