控释掺混肥结合增密对水稻氮肥利用效率和氨挥发的影响

为探究控释掺混肥结合增密对水稻产量、氮素吸收、施肥经济效益和氨挥发损失的影响，该研究以扬籼优418为供试材料，设不施氮对照（CK）、常规施氮（Farmer''s Fertilization Practice，FFP）、优化施氮（Optimized Nitrogen Application，OPT）、控释掺混肥（Controlled Release Blended Fertilizer，CRBF）和控释掺混肥结合增密（Controlled Release Blended Fertilizer Combined with Dense Planting，CRFDP）共5个处理，对比分析了不同处理的水稻产量及构成因子、氮素吸收和氮肥利用效率、经济效益和氨挥发损失的差异。结果发现，CRFDP处理的水稻有效穗数和每穗实粒数显著高于其他处理（P<0.05），较FFP分别增加26.1%和18.7%。CRFDP处理较FFP处理水稻增产33.3%。与FFP相比，CRFDP的氮肥吸收利用率、氮肥偏生产率、氮肥农学利用率分别提高160%、22.8 kg/kg、16.27 kg/kg。CRFDP较CRBF处理的氮肥吸收利用率显著提高10.0个百分点，氮肥偏生产率、氮肥农学利用率和氮素生理利用率则没有显著差异（P>0.05）；与FFP处理相比，3个优化施氮处理（OPT、CRBF和CRFDP）在氮肥用量降低20%的情况下，水稻每公顷净收益增加3 328～8 968元，其中CRFDP处理的水稻产值和净收益最高。施氮显著提高了水稻生长季的田面水铵态氮浓度和土壤脲酶活性，与FFP处理相比，CRFDP处理的氨挥发强度和累积氨挥发损失分别降低62.5%和46.3%。综上，控释掺混肥与增密结合可兼顾水稻高产、氮肥高效利用和氨减排。研究结果可为水稻高产及环境友好和资源高效的水稻种植新模式数据支持和理论支撑。

Effects of the blends of controlled-release and conventional nitrogen fertilizers combined with dense planting on nitrogen use efficiency and ammonia volatilization in a paddy field

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.