秸秆还田下节水减氮对不同双季稻品种N_(2)O排放的影响及驱动因素

Effects and driving factors of reduced nitrogen application and water-saving irrigation combined with straw returning on N_(2)O emission between two double-cropping rice varieties

为明确秸秆还田下节水减氮以及高效肥料对不同双季稻品种N_(2)O排放的影响及其关键驱动因素。于2020年开展田间试验,试验采用裂区设计,主区为4个水肥处理:尿素100%+间歇灌溉(U)、尿素80%+秸秆还田+间歇灌溉(US+S)、控释尿素80%+秸秆还田+间歇灌溉(CRUS+S)、尿素80%+秸秆还田+节水灌溉(US+S+SWD),副区为常规稻和杂交稻,共8个处理。监测双季稻生育期内N_(2)O排放规律,分析单位产量N_(2)O排放强度和影响其排放的主要驱动因素。结果表明,灌溉量、碳氮投入和植株吸氮量是调控稻田N_(2)O排放的主导因子,可解释99%的排放变化,其中氮投入增加会促进N_(2)O排放,而灌溉量、碳投入和吸氮量对N_(2)O排放有负向作用。秸秆还田可以补充氮肥减量20%的养分,秸秆还田下常规氮肥或控释氮肥减量施用降低了N_(2)O排放14.4%~49.4%,但CRUS+S较US+S处理促进了N_(2)O排放,表明秸秆还田下施用控释尿素并不能实现N_(2)O减排。秸秆还田后进一步控水促进了N_(2)O排放,相比US+S,US+S+SWD处理显著增加了双季稻N_(2)O的排放114.8%~186.4%,且常规稻增幅大于杂交稻。各处理间产量无显著差异,氮肥减量及进一步控水均可保证稳产,但US+S+SWD处理单位产量N_(2)O排放强度显著高于其他处理。总体而言,秸秆还田搭配减氮20%有助于降低稻田N_(2)O排放,但并不能抵消节水灌溉导致的N_(2)O增长。在水稻生产中合理利用秸秆资源,适当减少氮肥用量可以减少稻田N_(2)O排放并保证稳产。

In order to clarify the effects of water saving,nitrogen reduction,high efficiency fertilizer and straw returning on N_(2)O emission between rice varieties and their driving factors,a field experiment was carried out in 2020 to monitor N_(2)O fluxes during the growth period of double cropping rice,and to analyze yield-scaled N_(2)O emission and the main driving factors related to N_(2)O emission.Split plot design was adopted in the experiment with 8 treatments.The main plot consisted of four water and fertilizer treatments:urea 100%+intermittent irrigation(U),urea 80%+straw returning+intermittent irrigation(US+S),controlled release urea 80%+straw returning+intermittent irrigation(CRUS+S),urea 80%+straw returning+water-saving irrigation(US+S+SWD).The sub-plot factors were conventional rice and hybrid rice.The results showed that irrigation,carbon and nitrogen inputs,and plant nitrogen uptake were the leading factors regulating N_(2)O emission from rice fields,which could explain 99%of N_(2)O emission variations.Nitrogen input promoted N_(2)O emission,while irrigation,carbon inputs and nitrogen uptake had a negative effect on N_(2)O emission.Straw returning could supplement the reduced nutrients of 20%nitrogen fertilizer.Straw returning combined with conventional or controlled-release urea reduced N_(2)O emission by 14.4%-49.4%.However,CRUS+S treatment promoted N_(2)O emission compared with US+S treatment,indicating that straw returning combined with controlled-release urea could not achieve N_(2)O reduction in rice cultivation.Water-saving irrigation after straw returning to the field further promoted N_(2)O emission.Compared with US+S treatment,US+S+SWD treatment significantly increased N_(2)O emission of double cropping rice by 114.8%-186.4%,and the increase rate of conventional rice was higher than that of hybrid rice.There was no significant difference in yield among different treatments,and nitrogen reduction and water-saving irrigation could guarantee a stable yield.However,yield-scaled N_(2)O intensity of US+S+SWD treatment was significantly higher than that of other treatments.In general,straw returning combined with 20%reduction in nitrogen can reduce N_(2)O emissions from paddy fields,but can not offset the increase of N_(2)O caused by water-saving irrigation.Rational use of straw resources and reduction of nitrogen fertilizer application in rice production can help reduce N_(2)O emission and ensure stable yield.