Abstract:
Rice is one of the important staple food crops in China. Precision agricultural management can be critical to the high rice yield for national food and ecological security. Fortunately, the controlled-release fertilizer is a novel kind of nutrient-efficient and environment-friendly fertilizer. Better synchronizing the nitrogen (N) release and crop uptake can be utilized to promote the crop yield and nitrogen use efficiency (NUE), while reducing the reactive N losses. At the same time, moderate-density planting can be used to enhance the nutrient uptake by the rice plants, leading to reduce the nutrient losses and fertilizer application rate. This study aims to determine the effects of the blends of controlled-release and conventional N fertilizers combined with the dense planting on the rice yield, N uptake, economic benefits, and ammonia (NH3) volatilization. A paddy field experiment was also conducted to plant with the rice cultivar of Yangxianyou 418. Five treatments of N fertilizer management were established, including no N fertilizer (CK), conventional N fertilizer (FFP), optimized N fertilizer (OPT), blends of controlled-release and conventional N fertilizers (CRBF), as well as the blends of controlled-release and conventional N fertilizers combined with dense planting (CRFDP). Among them, the total N was applied all at once as the basal fertilization in the CRBF and CRFDP treatments. A comparison analysis was made on the rice yield, yield components, N uptake, NUE, economic benefits, and NH3 volatilization under different treatments. The highest numbers of effective panicles per plant and effective grains per panicle of rice plants were observed under the CRFDP, which were significantly (P<0.05) higher than those under the FFP by 26.1% and 18.7%, respectively. The CRFDP treatment significantly (P<0.05) increased the rice yield by 33.3%, compared with the FFP. Specifically, the N recovery efficiency (NRE), N agronomic efficiency (NAE), N partial factor productivity (NPFP), and significantly increased by 160%, 22.8 kg/kg, and 16.27 kg/kg, respectively, under the CRFDP, compared with the FFP. The NRE of CRFDP treatment was significantly (P<0.05) higher than that of CRBF by 10%, while there was no significant difference in the NAE, NPFP, and NPE. The optimized N fertilization treatments (OPT, CRBF, and CRFDP) increased the net economic benefits of rice by 3 328-8 968 yuan/hm2 with a 20% reduction in N application rate, compared with the FFP treatment. Besides, the CRFDP treatment presented the highest output value and net economic benefits among different optimized N fertilization treatments. The application of N fertilizer significantly increased the ammonium-nitrogen concentration in the surface water and soil urease activity in the paddy field during the rice growing season. The episodic and cumulative NH3 volatilization significantly (P<0.05) decreased by 62.5% and 46.3%, respectively, under the CRFDP, compared with the FFP. In conclusion, the blends of controlled-release and conventional N fertilizers combined with the dense planting can be expected to concurrently benefit the yield, NUE, and the reduced NH3 loss in the rice production system.