Abstract:

【Objective】 It is very important to explore chemical nitrogen fertilizer reduction and rationing to stabilize rice yield, improve nitrogen use efficiency, reduce the risk of nitrogen and phosphorus loss, and lay a scientific basis for fertilizer reduction in the Dongting Lake double-cropping rice area. 【Method】 The field plot experiment was conducted, and six treatments were set, including no nitrogen fertilizer (CK), conventional fertilizer (CF), 20% nitrogen reduction with borosilicate fertilizer (0.8CF+B/Si), 80% chemical fertilizer+20% organic fertilizer (0.8CF+0.2OM), 80% chemical fertilizer+20% organic fertilizer with nitrogen synergist (0.8CF+0.2OM+N-serve), and 20% organic fertilizer combined with borosilicate fertilizer and nitrogen synergist (0.8CF+0.2OM+B/Si+N-serve). Yield, nitrogen use efficiency, and the risk of nitrogen and phosphorus loss in field water of double-cropping rice were analyzed. 【Result】 The yield of early rice was reduced as compared with CF, while the yield of late rice was increased by 2.02% to 5.03%. The concentrations of total nitrogen, ammonium nitrogen, and nitrate nitrogen in surface water increased with the increase in nitrogen application rate, and the risk of nitrogen loss also increased. Compared with CF treatment, the chemical fertilizer nitrogen reduction and rationing treatment reduced total nitrogen, ammonium nitrogen, and nitrate nitrogen concentrations in early and late rice seasonal field water by 8.08% to 35.05%, 5.88% to 34.22%, and 5.02% to 18.06%, respectively, and 0.8CF+0.2OM+N-serve treatment was the most effective in mitigating the risk of nitrogen loss from field water. One week after nitrogen application was the peak period of nitrogen loss, and then the difference in nitrogen concentration in surface water of each treatment decreased, as did the risk of nitrogen loss. The phosphorus concentration of early and late rice surfaces without nitrogen fertilizer was lower than that of other treatments, while the phosphorus concentration of early and late rice surface water with borosilicate fertilizer was higher than that of other treatments, which aggravated the risk of phosphorus loss in rice surface water. In addition, the combined application of organic fertilizer and nitrogen fertilizer synergists had no obvious effect on phosphorus emission reduction. About 9 days after the application of phosphorus fertilizer was the key period of phosphorus loss, after which the phosphorus concentration of each treatment tended to be consistent and changed smoothly. 【Conclusion】 The substitution of organic fertilizer for nitrogen fertilizer has a lag effect on rice yield. The simultaneous application of nitrogenous synergists with organic fertilizers will weaken the effect of nitrogen synergists in retarding nitrogen fertilizer conversion. Chemical fertilizer nitrogen reduction and rationing is an effective method to reduce nitrogen loss in the surface water of double-cropping rice fields, but its combination with borosilicate fertilizer can increase phosphorus content in the surface water, so it should be applied according to water and fertilizer management.

Key words: rice, fertilizer application, nitrogen reduction, yield, surface water, nitrogen and phosphorus loss

摘要：

【目的】 探究化学氮肥减量配施稳定水稻产量，提高氮肥利用率，减少氮磷流失风险，为洞庭湖双季稻区化肥减量施用提供科学依据。【方法】 采用大田小区试验，设置不施氮肥(CK)、常规施肥(CF)、减氮20%配施硼硅肥(0.8CF+B/Si)、有机肥替代20%化学氮肥(0.8CF+0.2OM)、有机肥替代20%化学氮肥配施氮肥增效剂(0.8CF+0.2OM+N-serve)、有机肥替代20%化学氮肥配施硼硅肥和氮肥增效剂(0.8CF+0.2OM+B/Si+N-serve)共6个处理，研究化肥减氮配施对双季稻产量、氮肥利用率和田面水氮磷流失风险的影响。【结果】 有机肥替代处理早稻产量较CF均有一定下降，而晚稻产量提高2.02%~5.03%。田面水中总氮、铵态氮、硝态氮浓度随着氮肥施用量的增加而上升，氮素流失风险也增大。与CF处理相比，化肥减氮配施处理早晚稻季田面水总氮、铵态氮和硝态氮浓度分别降低8.08%~35.05%、5.88%~34.22%和5.02%~18.06%，有效降低田面水氮素流失风险，其中以0.8CF+0.2OM+N-serve处理效果最好。施氮肥后一周是氮素流失的高风险时期，随后各处理田面水氮素浓度差异变小且流失风险降低。不施氮肥处理的早、晚稻田面水磷素浓度低于其他处理，而配施硼硅肥处理高于其他处理，田面水中磷素的流失风险增大。此外，配施有机肥、氮肥增效剂对磷素减排效果不明显。施磷肥后9 d左右是磷素流失的关键时期，之后各处理磷素浓度趋于一致且变化平稳。【结论】 有机肥替代氮肥对双季稻增产存在一定滞后性；氮肥增效剂与有机肥同时施用会削弱其延缓氮肥转化的效果，影响养分吸收。化肥减氮配施是降低双季稻田面水氮素流失的有效方法，但配施硼硅肥会提高田面水磷素含量，应根据田间水肥管理酌情施用。

关键词: 水稻, 肥料配施, 减氮, 产量, 田面水, 氮磷流失