Characteristics and performance of water-adsorbent polymer coated urea

Absorbed fertilizers is new trend to research and development of slow/controlled release fertilizers(SRFs/CRFs). In this article, the author prepared water absorbent polymer coated urea (WACU) by using chemical polymerization reaction, and study coatings characteristics, performance of nutrient-controlling release, and effects of the coated urea on soil water. Test results of WACU show that the actual coating rate is lower than that of the designed coating rate of WACU, generally 10%12%. The photograph of SEM(Scanning Electronic Microscopy) show that there are lot of fiber-network-like porosity in coatings of fertilizers, the coatings is 0.15mm0.25 mm in thickness. The results of 7d water solution rate experiment indicate that the capability of nutrient-controlling release of WACU is inferior to that of plastic coated, or water adsorbent plus plastic coated urea, the slow release effect of WACU is mainly attributed to the absorption of urea by water absorbent. The measurement results of soil water characteristic curve show that WACU can increase water content and availability in soils treated by WACU, improve water-holding and releasing properties of soil. Thus, WACU is one of new slow/controlled release fertilizers that have the potential of development and application.