“紫云英×油菜”混播还田及减施氮肥对双季稻田温室气体排放的影响

Effects of Nitrogen Fertilizer Reduction on Greenhouse GasEmissions from Double-Cropping Paddy Fields under the MixedPlanting and Returning of Chinese Milk Vetch and Rapeseed

为探究绿肥“紫云英×油菜”混播还田及氮肥减施对双季稻田温室气体排放的影响,在冬季种植“紫云英×油菜”并还田的条件下,设双季稻不施氮肥(CK)、施100%氮肥(150 kg·hm^(-2),N1MR)、减施20%氮肥(120 kg·hm^(-2),N2MR)、减施40%氮肥(90 kg·hm^(-2),N3MR)和减施60%氮肥(60 kg·hm^(-2),N4MR)共5个处理。在双季稻生育期内平均每7 d采用静态暗箱—气相色谱法测定稻田温室气体排放,分析绿肥混播还田条件下氮肥减施对双季稻田水稻产量、温室气体排放通量、累积排放量、全球增温潜势(GWP)及温室气体排放强度(GHGI)的影响。结果表明,氮肥减施20%~40%能显著提高水稻产量,减施20%和40%处理水稻产量分别较CK显著提高24.2%和23.8%(P<0.05)。在双季稻生育期,所有施氮处理均较CK显著降低了CH_(4)排放,增加了N_(2)O排放(P<0.05)。氮肥减施20%处理的GWP和GHGI两季总量均为最低,且均显著低于CK、施100%、减施40%和减施60%氮肥处理(P<0.05),GWP分别降低57.9%、16.5%、23.4%和40.8%,GHGI分别降低63.9%、17.8%、24.6%和43.2%。综上,氮肥减施20%对水稻增产和温室气体减排效果最佳。因此,“紫云英×油菜”混播还田配合氮肥减施20%是一种适合当地推广的低碳稳产施肥管理模式。本研究结果为实现南方稻区农业绿色可持续发展提供了理论依据和决策基础。

This study was conducted to explore the effects of nitrogen fertilizer reduction and the Chinese milk vetch(CMV)+rapeseed mixed seeding and incorporation on greenhouse gas emissions in double-cropped paddy fields..The study was comprised of five different treatments,including double-cropping rice without nitrogen fertilizer(CK),100%nitrogen fertilizer(150 kg·hm^(-2),N1MR),20%reduction in nitrogen fertilizer(120 kg·hm^(-2),N2MR),40%reduction in nitrogen fertilizer(90 kg·hm^(-2),N3MR),and 60%reduction in nitrogen fertilizer(60 kg·hm^(-2),N4MR).The emission flux of CH_(4)and N_(2)O was determined by static dark box-gas chromatography in paddy fields,and discussed the effects of different N application rates under the mixed planting and returning of green manure on rice yield,Greenhouse gas emission flux,accumulation emission flux,global warming potential(GWP),and greenhouse gas emission intensity(GHGI).The results showed that 20%(N2MR)and 40%(N3MR)N fertilizer reduction increased rice yield by 24.2%and 23.8%,respectively,compared to control CK.Compared to CK,N application significantly(P<0.05)reduced CH_(4)emissions and increased N_(2)O emissions at the reproductive stage of double-cropping rice.The total GWP and GHGI in both seasons under N2MR substantially lower than CK(GWP 57.9%;GHGI 63.9%),N1MR(GWP16.5%,GHGI 17.8%),N3MRr(GWP 23.4%,GHGI 24.6%),and N4MR(GWP 40.8%,GHGI 43.2%)respectively.The N2MR treatment was the most effective in increasing rice yield and reducing greenhouse gas emissions.Therefore,applying N(120 kg·hm^(-2))with a mixture of CMV and rapeseed incorporation is a low-carbon and stable fertilization management model suitable for promotion.This provides a theoretical basis and decision-making foundation for achieving sustainable ecosystem development in the southern rice region of China.