Effects of different types of slow-and controlled-release fertilizers on rice yield

This experiment explored the effects of single application of seven types of slow-and controlled-release fertilizers on rice yield and various population characteristics. Based on a study of the nitrogen(N) release characteristics of these fertilizers, pot experiments were conducted in 2018 and 2019 with split fertilization(CK, urea applied split equally at basal and panicle initiation stages, respectively) as control, which assessed the effects on SPAD value, yield and yield components, dynamic changes of rice tillers and dry matter accumulation. The results showed that the N release characteristics of different types of slow-and controlled-release fertilizers were significantly different. Polymer-coated urea(PCU) showed a controlledrelease mode and provided sustained release throughout the whole growth stages. Sulfur-coated urea(SCU) exhibited a slow-release mode, providing insufficient release at the middle and late stages. Urease inhibitor urea(AHA) and ureaformaldehyde(UF) yielded a rapid-release mode, with an explosive N release at the early stage and no release at the middle and late stages. These results showed that PCU delayed the peak seedling stage. Compared with CK, dry matter accumulation and SPAD showed no significant differences, and due to the continuous release of N throughout the growth stages, rice yield, spikelets per panicle, seed setting rate, and 1 000-grain weight were all increased. Owing to the lack of N supply at the late stage and the low number of spikelets, SCU led to a reduction of rice yield, which is nevertheless not statistically significant. AHA and UF were susceptible to environmental factors and had varying effects on rice yield. The results of this experiment indicated that given a fixed amount of N applied in a pot, the stronger the N supply capacity and the longer the effective duration time of the fertilizer, the higher the dry matter accumulation at the late growth stage, and the higher the rice yield.