This paper studied the effects of the coating thickness and granular diameter on the nitrogen release rate to select a treatment of controlled release fertilizer(CRF) which consumed less coating material but had better controlling effect to realize the purpose to reduce the cost of CRFs.The results of this experiment showed that

CRF of 2.5~3 mm diameter had the best coating effect than 3~4 mm and 4~5 mm diameters;When the coating thickness was 60 g/m2 and 70 g/m2 respectively

the release rate of CRFs of 3~4 mm diameter was mild

and its release period was longest than others diameters(2.5~3 mm

4~5 mm diameter).The capability of nutrient-controlling release of 3~4 mm diameter was better to that of 2.5~3 mm diameter and 4~5 mm diameter too;The result of effect of coating thickness on characteristics of nitrogen release was that preliminary solubility

differential solubility and nitrogen accumulated release rate all had decrease tendency remarkably with the increase of coating thickness.Among the results

effect of coating thickness on 3~4 mm diameter was best than other two diameter treatments

however on 4~5 mm diameter was smallest.