Effects of integral regulation and control of super absorbent polymer coated urea on water and fertilizer use efficiencies

A series of products of super absorbent polymer(SAP) coated urea(SAPCU) with single membrane of SAP or with duplex membranes of modified mineral inside and SAP outside were developed by using different types and different water absorbent rates of SAPs as coating material, and big granule urea and modified mineral coated urea as the core fertilizers. A pot experiment of corn was carried out to study the effects of integral regulation and control of SAPCUs on water and fertilizer use efficiencies under nutrient leaching and water stress conditions. The result showed that SAPCUs could obviously decelerate N release, reduce N amount of leaching loss and decrease water amount used. As the ratios of SAP to Core Fertilizer were 6∶100 and 9∶100, the corn biomass, water and fertilizer use efficiencies of SAPCU treatment were significantly increased compared with those of core fertilizers. The effects of integral regulation and control of SAPCUs on water and fertilizer use efficiencies were mainly related to membrane, properties of inner membrane, types of SAP and their use levels. The inner membrane of SAPCUs with duplex membranes could obviously increase the effects of nutrients controlled/slow release, and SAPCUs with duplex membranes had better fertilizer effect than that of SAPCUs with single membrane. The material of inner membrane, which had a less influence on water absorbent rate of SAP and could absorb and fix nutrient ions, had a better effect. For all SAPCUs, the effects were more noticeable with the increase of SAPs use level.