不同秸秆还田形式对节水灌溉减施氮肥稻田碳氮足迹的影响

Effects of Different Straw Returning Modes on Carbon and Nitrogen Footprints in Paddy Fields under Water-saving Irrigation and Nitrogen Reduction Application

摘要:

为明确寒地黑土区不同秸秆还田形式对节水灌溉减施氮肥稻田碳氮足迹的影响,本文采用生命周期评价法(LCA),以FS0N1(常规淹灌+无秸秆还田+常规施氮水平)作为对照,设置DS0N1(浅湿干灌溉+无秸秆还田+常规施氮水平)、DS1N2(浅湿干灌溉+秸秆100%直接还田+氮肥减施10%)、DS2N2(浅湿干灌溉+秸秆100%炭化还田+氮肥减施10%)、DS3N2(浅湿干灌溉+秸秆50%直接还田+秸秆50%炭化还田+氮肥减施10%)、DS1N3(浅湿干灌溉+秸秆100%直接还田+氮肥减施20%)、DS2N3(浅湿干灌溉+秸秆100%炭化还田+氮肥减施20%)、DS3N2(浅湿干灌溉+秸秆50%直接还田+秸秆50%炭化还田+氮肥减施20%)等处理,观测稻田CH4、N2O排放量和NH3挥发量等数据,计算不同秸秆还田形式下节水灌溉稻田碳氮足迹及构成,并分析碳氮足迹间的关系。结果表明：水稻生产单位面积碳足迹(CFA)、单位产量碳足迹(CFY)、碳效率(CE)分别为6 694.56~14 042.32 kg/hm^2、0.77~1.61 kg/kg、0.62~1.29 kg/kg,单位面积氮足迹(NFA)、单位产量氮足迹(NFY)分别为12.55~17.13 kg/hm^2、1.41~2.10 g/hm^2;节水灌溉减施氮肥条件下秸秆炭化还田可以降低CFA、CFY、NFA、NFY,同时增加CE;而秸秆直接还田会增加CFA、CFY、NFA、NFY,同时降低水稻产量和CE;水稻产生碳足迹占比中CH4排放(65.3%～81.3%)最大,其次是化肥(7.2%～13.6%),然后是柴油(3.1%～6.5%)和灌溉用电(2.6%～4.4%),氮足迹占比从大到小依次为NH3挥发(72.3%～79.7%)、农资农事投入(9.9%~17.1%)、NO3-N淋失(5.2%～6.1%)、N2O排放(2.8%~3.5%);不同秸秆还田形式下节水灌溉稻田的CFY与NFY呈正相关关系。其中DS2N2处理最优,其碳氮足迹最小,且产量最高。研究结果可为国家或区域农业碳氮足迹核算提供可靠数据支撑。

Abstract:

In order to clarify the effects of different straw returning forms on the carbon and nitrogen footprint of paddy fields under water-saving irrigation and nitrogen fertilizer reduction application in the cold and black soil region,the life cycle assessment method (LCA) was used,and FS0N1 (conventional flooding irrigation + no straw returning + conventional nitrogen application level) was used as a control. Treatments of DS0N1 (dry-wet-shallow + no straw returning + conventional nitrogen application level),DS1N2 (dry-wet-shallow + straw 100% direct returning + nitrogen fertilizer reduction by 10%),DS2N2 (dry-wet-shallow + straw 100% carbonization + nitrogen fertilizer reduction by 10% ),DS3N2 (dry-wet-shallow + straw 50% direct returning + straw 50% carbonization + nitrogen fertilizer reduction by 10%),DS1N3 (dry-wet-shallow + straw 100% direct returning + nitrogen fertilizer reduction by 20%),DS2N3 (dry-wet-shallow + straw 100% carbonization + nitrogen fertilizer reduction by 20%),and DS3N2 (dry-wet-shallow + straw 50% direct returning + straw 50% carbonization + nitrogen fertilizer reduction by 20%) were set. CH4,N2O emissions and NH3 volatilization in paddy fields were observed,and the carbon size and composition of carbon and nitrogen footprints in water-saving irrigation paddy fields under different straw returning forms were calculated,and the relationship between carbon and nitrogen footprints was analyzed. The results showed that the carbon footprint per unit area (CFA),carbon footprint per unit yield (CFY) and carbon efficiency (CE) were 6 694.56~14 042.32 kg/hm^2,0.77~1.61 kg/kg and 0.62~1.29 kg/kg,respectively. The nitrogen footprint per unit area (NFA) and nitrogen footprint per unit yield (NFY) were 12.55~17.13 kg/hm^2 and 1.41~2.10 g/hm^2,respectively. Under the condition of water-saving irrigation and nitrogen fertilizer reduction,straw carbonization returning to the field can reduce CFA,CFY,NFA,NFY,and increase CE;straw returning directly to the field would increase CFA,CFY,NFA,NFY,while reducing rice yields and CE;CH4 emission (65.3%~81.3%) was the largest in the proportion of carbon footprint generated by rice,followed by chemical fertilizer (7.2%~13.6%),diesel oil (3.1%~6.5%) and irrigation electricity (2.6%~4.4%). The proportion of nitrogen footprint from large to small was NH3 volatilization (72.3%~79.7%),agricultural inputs (9.9%~17.1%),NO3-N leaching (5.2%~6.1%),and N2O emissions (2.8%~3.5%). There was a positive correlation between CFY and NFY in water-saving irrigation paddy fields under different straw returning forms. Among them,DS2N2 treatment was the best,with the smallest carbon and nitrogen footprint and the highest yield. The research results can provide reliable data support for national or regional agricultural carbon and nitrogen footprint accounting.