Polymer-Coated Tablet Urea Improved Rice Yield and Nitrogen Use Efficiency

The high cost of coating materials prevents the wide use of controlled release urea (CRU). A large size polymer-coated tablet urea (PCTU) can be produced with <30% of coating materials used for traditional size of CRUs. The objective of this experiment was to evaluate the effects of a PCTU produced in our laboratory on root growth, grain yield, and N use efficiency on rice (Oryza sativa L.) grown in a silt loam soil during two growing seasons. The PCTU, regular CRU and urea formaldehyde (UF) were applied into the soil one time before transplanting at the rate of 0.93 g N pot(-1), while the conventional urea (U) treatment was applied three times in the tillering (40%), jointing (30%), and heading stages (30%). The results showed that the PCTU treatment produced higher root vigor, peroxidase activity, and yield of rice than the U treatment. There was no significant difference in plant height, SPAD value, growth indexes of plant shoot and root of rice among the PCTU and U treatments in the rice tillering stage, but splitting applications of U at tillering, jointing, and heading stages costs more for labor and machinery than applying once for PCTU. The PCTU treatment increased the yield of grain and total N use efficiency more than the U, CRU, and UF treatments did, but the UF treatment produced the highest yield and N use efficiency of straw.