Rice yield as affected by the split method of 'N' application and nitrification inhibitor DCD

Abstract. Large quantities of N fertilizers may be lost in rice fields by nitrification-denitrification. In this connection, experiments were carried out in order to compare the effects from slow-release N-fertilizers (ISODUR) and products integrated with diciandiamide (DCD), a nitrification inhibitor, with the N splitting method applied in two or three times on the rice growth and yield. The effect of increasing N rate at preplant time compared with the topdressing application was also determined. Experiments were conducted for 2 years on a typical Po Valley sandy soil. Fertilizers treatments were applied on two commercial rice cultivars, Baldo and Panda, using a split-plot design. Fertilizer treatments replicated four times were main plots; and cultivars were subplots. Different types of N fertilizers through two years experiments were compared with N split applications based on two or three times. Plant growth (height), plant development (days to heading and ripening), rice yield, yield components, and quality were monitored. Results showed that split fertilization with N topdressed at panicle initiation stage was more effective in rice yielding than preplant only application, independently from the N rate. Commercial “slow-release” fertilizer and ammonium sulphate were less effective in rice production. Compared to urea, inhibitor of nitrification, Diciandiammide (DCD) was the top yielding treatment, when applied with the split method. The fertilization method, based on three split N applications, showed no significant yielding differences compared to the two times method.