Preparation of Clay based Slow-release Fertilizers Containing Nitrogen,Phosphorus and Potassium and its Release Characteristics

[Objective] It was an effective way to improve the utilization efficiency of release fertilizer using clay as a carrier for preparation of nitrogen,phosphorus,and potassium fertilizer.[Method] A variety of clay-based nitrogen,phosphorus,potassium fertilizer and their complex fertilizers were prepared by grinding methods using bentonite and kaolin as supporters.Release characteristic curves of nitrogen,phosphorus and potassium were obtained by the leaching experiments.[Result] Compared with the traditional fertilizers,the release performances of nitrogen,phosphorus and potassium using bentonite and kaolin as supporters were better.Moreover,bentonite was superior to kaolin.The reason was that the charge disbalance within layer sheets of bentonite,and there was a large number of broken bonds in the edge of bentonite,then a large expansion space after hydration,which made nitrogen,phosphorus and potassium were locked in the interlayer of bentonite,and wouldn't lose easily.Nitrogen,phosphorus and potassium of bentonite based complex fertilizer CLAY-NPK had a good slow-release property.The release rate of nitrogen was the fastest,followed by potassium,and phosphorus was the slowest.[Conclusion] Research on the slow-releasing characteristics of nitrogen,phosphorus,and potassium fertilizer based bentonite had a great value for the production and the usage of release fertilizer.