Polymer-Coated Tablet Urea Improved Growth, Grain Yield And Nitrogen Use Efficiency Of Rice

The polymer-coated table urea(PCTU) is one of polymer coated controlled-release fertilizer developed by Shandong Agriculture University, and the advantages of TPCU could be: big fertilizer granule, small specific surface area, save coating materials, and lower cost. The different influences of PCTU, others N fertilizers and urea mixed with dicyandiamide(DCD) were investigated in the experimental field of Shandong Agricultural University during the growing season of 2012 and 2013. The study included four experiments: The cumulative N release rate of PCTU and controlled-release urea(CRU) in water at 25℃; Effects of PCTU, CRU, urea(U) and urea formaldehyde(UF) on the growth of rice during the tillering stage; Effects of application of PCTU, CRU, UF, U and DCD at different N levels(100, 220, 300 kg N ha-1) on the growth of rice plant; Effects of PCTU applied at different depth and placement methods on the growth of rice. The objective of our study is to provide a scientific basis for constituting and optimizing the use scheme of PCTU in future agriculture and afford technical suooprt for popularization and mechanical application of PCTU. The main results were as followed:1. The longevity of PCTU and CRU were three and six months respectively, and all the PTCU and CRU were fit for the requiements of standard of controlled-release fertilizer(GB/T 23348-2009).2. PCTU had the higher value of root vigor, root POD activity, soil urease and soil phosphatase than U treatment, but it was not significantly different in rice plant height, SPAD value and other index of root and shoot compaired with U treatment at the rice tillering stage. The N release of PCTU could meet the growth of rice in the early stage. Meanwhile, CRU were higher in plant height, SPAD value, dry weight and fresh weight of root, the reason was that the N release of CRU was faster than that of PCTU during the rice tillering stage.3. The differences of yield of rice affected by different N fertilizer sources with different N levels were significant. The PCTU produced more yield of grain and improved higher N use efficiency of grain and total N use efficiency than others, but UF and DCD treatments had more yield of straw and higher N use efficiency of straw than others. As a whole, the N use efficiency of rice applied with controlled-/ slow-release N fertilizers and DCD were higher than U treatment.4. With the increasing of the quantity of N fertilizers, the yield, plant height and SPAD value of rice would be increased, but the N use efficiency of grain and straw and total N use efficiency of rice were decreased. It indicated that the treatment applied N fertilizer at middle N level(220kg N ha-1) could have the higher yield and N use efficiency than other N levels.5. The plant height and SPAD value were influenced significantly by the different N fertilizer sources and rates. The higher plant height and SPAD value in PCTU were obtained at mid-late development stage of rice, but the CRU could increase the plant height and SPAD value of rice during the early-middle development stage.6. It was not significant that the growth, yield and N use efficiency of rice when the PCTU was applied at different placement mentods in the soil. But the PCTU treatment applied at 15 depth in the soil and near theroots system had little better effect on growth and higher yield and N use efficiency of rice than others application methods.