氮肥和秸秆还田方式对麦玉轮作土壤N2O排放的影响

为探究氮肥和秸秆还田方式对N₂O排放的影响,本研究在关中地区冬小麦-夏玉米轮作模式下,采用双因素裂区设计,主区为常规施氮(G)和减量施氮(70%G);副区为秸秆不还田(N)、秸秆还田(S)和秸秆还田+生物炭(SB),分析对N₂O排放和产量的影响及与相关影响因子间的关系.结果表明,小麦季和玉米季各处理在施肥后第5～16d内相继出现N₂O排放高峰,在降雨后也出现N₂O排放峰值.N₂O通量和土壤温度、NH₄⁺-N含量呈显著正相关.在同等施氮水平下,S处理增加了N₂O排放量,SB处理可降低N₂O排放量,S和SB处理均能显著增加作物产量,且SB增产幅度更大; 70%G水平的N₂O年排放量较G水平减少了40%～48%,而产量并没有明显减少.综合考虑,在常规施氮基础上减氮30%配合秸秆+生物炭,在保证作物高产的同时,N₂O减排效果最好.     

椰糠生物炭对热区双季稻田N2O和CH4排放的影响

基于稻菜轮作模式,选择海南双季稻田为对象进行氧化亚氮（N₂O）和甲烷（CH₄）排放的原位监测,探究椰糠生物炭对该系统稻田温室气体排放的影响.试验设当地常规施肥对照（CON）、氮肥配施20 t·hm^-2生物炭（B1）、氮肥配施40 t·hm^-2生物炭（B2）及不施氮对照（CK）4个处理,采用静态箱-气相色谱法监测整个水稻种植季稻田N₂O和CH₄排放,并估算增温潜势（GWP）和温室气体排放强度（GHGI）.结果表明,早稻季N₂O排放动态与土壤矿质氮含量密切相关,排放集中在水稻苗期与分蘖期施肥后,各处理早稻季N₂O累积排放量为0.18~0.76 kg·hm^-2,相较于CON处理,生物炭处理减排18%~43%,其中B2处理达显著水平;生物炭可能通过促进N₂O的还原减少早稻苗期N₂O排放;提高土壤硝态氮含量而增加了早稻分蘖期N₂O排放.晚稻季N₂O排放集中在抽穗期和成熟期,累积排放量为0.17~0.34 kg·hm^-2,B1处理减排37%,B2增加3%,差异均不显著.稻田CH₄排放高峰出现在早稻季后期与晚稻季前期.各处理早稻季CH₄累积排放量为3.11~14.87 kg·hm^-2,CK较CON处理增排39%,生物炭处理可能提高土壤通气性限制早稻季产CH₄能力,B1和B2处理分别较CON减排28%和71%;晚稻季CH₄累积排放量为53.1~146.3 kg·hm^-2,排放动态与NH₄⁺-N含量极显著正相关,CK和B1分别较CON处理增加52%和99%,B2处理显著增加176% CH₄排放.早稻季B1和B2处理较CON分别增产12.0%和14.3%,晚稻季分别增产7.6%和0.4%.由于晚稻季甲烷排放的增加,施用生物炭增加了双季稻田总增温潜势（GWP）,其中高量生物炭达显著水平;不同施用量生物炭对双季稻田温室气体排放强度（GHGI）无显著影响.椰糠生物炭在热区稻田温室气体减排方面的应用仍需进一步研究.     

施用不同污泥堆肥品对土壤温室气体排放的影响

通过田间试验,分别施加两种不同的污泥堆肥品（A：含生物质炭堆肥品,B：不含生物质炭堆肥品）和不同施肥量,分析土壤CO₂、CH₄和N₂O动态变化特征和排放系数,研究施用污泥堆肥品对土壤温室气体排放的影响.结果表明,土壤CO₂和CH₄排放主要集中在生长期,生物质炭堆肥品低施用量能减少CO₂排放,而高施肥量增加CO₂排放.CH₄排放主要为负值,总体表现为土壤吸收CH₄,对照处理吸收量远高于其他处理（P<0.01）,A组处理CH₄吸收量随施肥量的增加而增加（P<0.05）.N₂O排放集中在发芽期和幼苗期,施肥量越高,排放量越大（P<0.01）.污泥堆肥品农用过程排放的温室气体主要是N₂O,施用A、B两种污泥堆肥品的土壤N₂O排放系数分别为1.02%~1.90%和1.28%~2.93%.生物质炭堆肥品具有显著的碳减排效果,其温室气体排放量比不含生物质炭堆肥品的土壤低19.49%~35.56%,且对于N₂O的减排效果较CH₄更为显著.     

Emissions of N2O and NH3, and nitrogen leaching from direct seeded rice under different tillage practices in central China

Tillage practices affect the fate of fertilizer nitrogen (N) through influencing transformations of N, but few studies have examined N₂O and NH₃ emissions, and N leaching from different rice tillage systems. Thus the objective of this study was to assess N₂O emission, NH₃ volatilization and N leaching from direct seeded rice in conventional tillage (CT) and no-tillage (NT) production systems in the subtropical region of China during the 2008 and 2009 rice growing seasons. Treatments were established following a split-plot design of a randomized complete block with tillage practices as the main plot and N fertilizer level as the sub-plot treatment, and there were four treatments: NT + no fertilizer (NT0), CT + no fertilizer (CT0), NT + compound fertilizer (NTC) and CT + compound fertilizer (CTC), respectively. Results showed that N fertilization significantly increased (p < 0.01) N₂O emissions, NH₃ volatilization and N leaching from rice fields in both years. In general, there was no significant difference in N₂O emissions and NH₃ volatilization between NT0 and CT0 in both years, while NTC had significantly higher (p < 0.05) N₂O emissions and NH₃ volatilization compared to CTC. Over the two rice growing seasons, NTC showed 32% and 47% higher N₂O emissions, and 29% and 52% higher NH₃ losses than CTC. Higher (p < 0.05) N₂O emissions from NTC than CTC were presumably due to higher soil organic C and greater denitrification. Total N and NO₃^? concentrations were higher (p < 0.05) in CTC than NTC, but larger volumes of percolation water in NTC than CTC resulted in no significant difference in leakage of total N and NO₃^?. Hence, application of N fertilizer in combination with NT appeared to be ineffective in reducing N losses from N fertilizer in paddy fields.     

不同用量竹炭对污泥堆肥过程温室气体排放的影响

采用城市污泥为堆肥基质,设置4个堆肥处理,分别为添加2.5%竹炭(S1,占污泥的质量分数)、添加5%竹炭(S2)、添加10%竹炭(S3)和未添加竹碳(CK),研究城市污泥堆肥过程中温室气体的动态变化特征及添加不同用量竹炭的影响.结果表明,CH_4排放主要在升温期和高温前期,占排放总量的99.01%~99.81%.当竹炭添加量低于5%时,CH_4排放量随添加量的增加而减少;竹炭添加量高于5%时,其排放量又明显增加.CO_2排放集中在升温期和高温期,占排放总量的75.65%~86.58%;添加竹炭可减少3.37%~13.48%的CO_2排放,但处理间不存在显著差异(P0.05).N_2O排放集中在升温期和降温腐熟期,添加竹炭能减少16.37%~41.52%的N_2O排放,竹炭添加量越多,减排效果越好(P0.05).S1、S2和S3处理CO_2排放当量(以干污泥计)分别为37.57、35.10和35.44 kg·t~(-1),比CK处理减少了14.81%~20.41%.添加竹炭能降低污泥堆肥温室气体排放,其中,以S2处理的减排效果较为显著.     

生物炭对潜流人工湿地污染物去除及N2O排放影响

生物炭作为一种生物质废弃物的热解产物,逐渐被应用于受污染水体治理.生物炭具有提高孔隙、吸附氮磷、控制温室气体排放等作用.通过在温室内构建生物炭投加比为40%、30%、20%、10%和0%的微型潜流湿地系统(分别命名为BW-40、BW-30、BW-20、BW-10和CW-K),探究生物炭投加对湿地污染物去除及N_2O排放的影响.结果表明,投加生物炭可以提高出水氧化还原电位(oxidation-reduction potential,ORP),降低电导率(conductivity,Cond),但影响均不显著(P 0. 05).5组湿地系统中化学需氧量(COD)去除率均达到90%,但随着生物炭投加比的增加,氨氮(NH_4~+-N)和总氮(TN)的去除效果显著提高(P 0. 05).湿地NH_4~+-N平均去除率为(34. 76±14. 16)%～(57. 96±10. 63)%,TN平均去除率为(70. 92±5. 68)%～(80. 21±10. 63)%.各湿地系统N_2O的平均释放通量在13. 53～45. 30 mg·(m~2·d)~(-1)之间,生物炭投加可以通过减少亚硝态氮(NO_2~--N)累积浓度和积累时间,实现N_2O减排,并显著减少湿地中N_2O排放占TN去除的百分比(P 0. 05). 40%的生物炭投加比可以实现70. 13%的N_2O减排效果.     

Managing the nitrogen cycle to reduce greenhouse gas emissions from crop production and biofuel expansion

Public policies are promoting biofuels as an alternative to fossil fuel consumption in order to mitigate greenhouse gas (GHG) emissions. However, the mitigation benefit can be at least partially compromised by emissions occurring during feedstock production. One of the key sources of GHG emissions from biofuel feedstock production, as well as conventional crops, is soil nitrous oxide (N₂O), which is largely driven by nitrogen (N) management. Our objective was to determine how much GHG emissions could be reduced by encouraging alternative N management practices through application of nitrification inhibitors and a cap on N fertilization. We used the US Renewable Fuel Standards (RFS2) as the basis for a case study to evaluate technical and economic drivers influencing the N management mitigation strategies. We estimated soil N₂O emissions using the DayCent ecosystem model and applied the US Forest and Agricultural Sector Optimization Model with Greenhouse Gases (FASOMGHG) to project GHG emissions for the agricultural sector, as influenced by biofuel scenarios and N management options. Relative to the current RSF2 policy with no N management interventions, results show decreases in N₂O emissions ranging from 3 to 4 % for the agricultural sector (5.5–6.5 million metric tonnes CO₂?eq.?year^?1; 1 million metric tonnes is equivalent to a Teragram) in response to a cap that reduces N fertilizer application and even larger reductions with application of nitrification inhibitors, ranging from 9 to 10 % (15.5–16.6 million tonnes CO₂?eq.?year^?1). The results demonstrate that climate and energy policies promoting biofuel production could consider options to manage the N cycle with alternative fertilization practices for the agricultural sector and likely enhance the mitigation of GHG emissions associated with biofuels.     

有机无机肥配施对不同程度盐渍土N2O排放的影响

选取内蒙古河套灌区轻度盐渍土S_1(EC为0.46 dS·m~(-1))及中度盐渍土S_2(EC为1.07 dS·m~(-1))为研究对象,在等施氮量条件下,采用静态箱-气相色谱法研究了不同有机无机肥配施比例:CK(不施肥)、U_1(240 kg·hm~(-2)化肥)、U_3O_1(180 kg·hm~(-2)化肥+60 kg·hm~(-2)有机肥)、U_1O_1(120 kg·hm~(-2)化肥+120 kg·hm~(-2)有机肥)、U_1O_3(60 kg·hm~(-2)化肥+180 kg·hm~(-2)有机肥)和O_1(240 kg·hm~(-2)有机肥)对春玉米农田土壤N_2O排放的影响,旨在明确不同施肥策略下土壤N_2O排放特征,为制定盐渍化农田合理的减排措施提供理论依据.结果表明, 2种不同程度盐渍化土壤N_2O排放存在显著差异,同一处理S_2土壤N_2O排放总量较S_1土壤高出11.86%～47.23%(P0.05).各施肥处理对土壤N_2O排放通量影响趋势基本一致,即施肥后出现排放高峰,基肥和追肥后累积排放量占整个生育期排放量60%左右.适当施入有机肥可以显著降低土壤N_2O排放,S_1和S_2盐渍土分别以U_1O_1及O_1处理N_2O排放量最小,较U_1处理显著降低33.62%和28.51%(P0.05),同时可以获得较高的玉米产量.各施肥处理N_2O排放通量与土壤NH~+_4-N呈极显著正相关关系(P0.01),而与土壤NO~-_3-N含量呈负相关关系,表明硝化作用是盐渍化玉米农田N_2O产生的主要途径,配施有机肥可以持续减少土壤NH~+_4-N供给而减少N_2O的排放.从玉米产量及减少温室效应的角度,得到本地区适宜的施肥管理模式:轻度盐渍土为120 kg·hm~(-2)有机肥+120 kg·hm~(-2)化肥,中度盐渍土为240 kg·hm~(-2)有机肥.     

厌氧条件下砂壤水稻土N2、N2O、NO、CO2和CH4排放特征

了解厌氧条件土壤反硝化气体(N2、N2O和NO)、CO2和CH4排放特征,是认识反硝化过程机制的基础,并有助于制定合理的温室气体减排措施.定量反硝化产物组成,可为氮转化过程模型研发制定正确的关键过程参数选取方法或参数化方案.本研究选取质地相同(砂壤土)的两个水稻土为研究对象,通过添加KNO3和葡萄糖的混合溶液,将培养土壤的初始NO-3和DOC含量分别调节到50 mg·kg-1和300 mg·kg-1,采用氦环境培养-气体及碳氮底物直接同步测定方法,研究完全厌氧条件下土壤N2、N2O、NO、CO2和CH4的排放特征,并获得反硝化气态产物中各组分的比率.结果表明,在整个培养过程中,两个供试土壤的N2、N2O和NO累积排放量分别为6~8、20和15~18 mg·kg-1,这些气体排放量测定结果可回收土壤NO-3变化量的95%~98%,反硝化气态产物以N2O和NO为主,其中3种组分的比率分别为15%~19%(N2)、47%~49%(N2O)和34%~36%(NO);但反硝化气体产物组成的逐日动态均显现为从以NO为主逐渐过渡到以N2O为主,最后才发展到以N2为主.以上结果说明,反硝化气体产物组成是随反硝化进程而变化的,在以气体产物组成比率作为关键参数计算各种反硝化气体产生率或排放率的模型中,很有必要重视这一点.     

The role of CH4 and N2O emission reductions in the cost-effective control of the greenhouse gas emissions from Finland

The reduction of carbon dioxide (CO₂) emissions may be quite expensive and it is necessary to consider reduction measures for other anthropogenic greenhouse gases, such as methane (CH₄) and nitrous oxide (N₂O) as well. Their contribution to the total GHG emission from Finland is about 15–20%. In Finland most of the CH₄ emissions are due to waste management, agriculture and burning processes. N₂O emissions originate from burning processes, agriculture, industry and atmospheric deposition of nitrogen. The cost-effective reduction of the Finnish GHG emissions has been studied with the EFOM-ENV model, which is a quasi-dynamic linear energy system optimisation model. The target function to be minimised is the total discounted cost for the modelled system. In this study the model has been expanded to cover all well-known anthropogenic CO₂, CH₄ and N₂O sources and reduction measures. The results indicate it is economic to reduce the emissions of CO₂, CH₄ and N₂O in Finland. It is profitable to exploit the economic reduction potential of CH₄ and N₂O, because then the abatement of CO₂ emissions does not need to be as extensive as when the reduction is aimed only at CO₂ emissions. The inclusion of CH₄ and N₂O decreases the annual reduction costs about 20% in the year 2010.     

污水生物处理实际工艺中氧化亚氮的释放：现状与挑战

介绍了污水生物处理过程中N2O的产生途径,重点分析了污水厂典型脱氮工艺的N2O释放差异及其原因,提出了城市污水脱氮处理过程N2O减排的具体措施,并估算出全国城镇污水处理厂2011年N2O释放总量约为1.26×109g(以N计),对今后关于城市污水脱氮处理过程N2O产生及减排的研究趋势进行了评估.     

生物炭添加对半干旱地区土壤温室气体排放的影响

为确定生物炭添加对半干旱地区农田土壤温室气体释放的影响,采用小区定位试验,利用锯末(J)和槐树皮(H)及3种添加比例(1%、3%、5%,质量百分比),研究了生物炭添加6个月内表层土壤CO2、CH4和N2O等3种温室气体排放的动态变化.结果表明,与对照相比,各处理土壤CO2排放通量随生物炭的添加呈现增加的趋势,锯末和槐树皮等两种生物炭处理的土壤CO2平均排放通量分别增加了1.89%和3.34%,但差异不显著.CH4排放随着生物炭添加量的增加而降低,各生物炭处理的土壤表层CH4排放量平均降幅分别为:J1:1.17%、J3:2.55%、J5:4.32%、H1:2.35%、H3:5.83%、H5:7.32%.其中,锯末生物炭仅在5%添加量时较对照差异显著(P0.05),而槐树皮生物炭处理在3%和5%的添加量与对照差异均达显著水平(P0.05).生物炭对N2O的排放影响没有明显规律性.研究表明,生物炭在短期内对半干旱地区农田土壤CO2和N2O的排放没有显著影响,而对CH4排放则影响显著(P0.05).就生物炭类型而言,槐树皮生物炭在抑制CH4排放方面优于锯末生物炭,差异显著(P=0.048).     

Effects of aeration method and aeration rate on greenhouse gas emissions during composting of pig feces in pilot scale

The aim of this study was to uncover ways to mitigate greenhouse gas(GHG) emissions and reduce energy consumption during the composting process. We assessed the effects of different aeration rates(0, 0.18, 0.36, and 0.54 L/(kg dry matter(dm)·min)) and methods(continuous and intermittent) on GHG emissions. Pig feces and corn stalks were mixed at a ratio of 7:1. The composting process lasted for 10 weeks, and the compost was turned approximately every 2 weeks. Results showed that both aeration rate and method significantly affected GHG emissions. Higher aeration rates increased NH3 and N2O losses,but reduced CH4 emissions. The exception is that the CH4 emission of the passive aeration treatment was lower than that of the low aeration rate treatment. Without forced aeration,the CH4 diffusion rates in the center of the piles were very low and part of the CH4 was oxidized in the surface layer. Intermittent aeration reduced NH3 and CH4 losses, but significantly increased N2 O production during the maturing periods. Intermittent aeration increased the nitrification/denitrification alternation and thus enhanced the N2 O production. Forced aeration treatments had higher GHG emission rates than the passive aeration treatment. Forced aeration accelerated the maturing process, but could not improve the quality of the end product. Compared with continuous aeration, intermittent aeration could increase the O2 supply efficiency and reduced the total GHG emission by 17.8%, and this reduction increased to 47.4% when composting was ended after 36 days.     

农田土壤N2O产生的关键微生物过程及减排措施

氧化亚氮(N2O)作为一种重要的温室气体,其全球排放总量仍然在持续上升.它不仅可以产生温室效应,还可以间接破坏臭氧层,使其在全球气候变化和生态环境变化研究中备受关注.土壤生态系统是大气中N2O的最重要排放源.本文详细论述了农田土壤中反硝化作用、硝化作用、硝化微生物的反硝化作用以及硝酸盐异化还原成铵作用等过程产生N2O的微生物学机制,并从土壤理化性质(土壤pH、氮素、有机质、土壤温度和湿度)和土壤生物等方面对农田土壤N2O排放的影响进行综述,在此基础上对农田土壤N2O的减排措施进行总结,并就今后农田土壤N2O排放的研究重点和方向进行了展望,为调控农田土壤温室气体排放、氮转化过程和提高氮素利用效率提供科学依据.     

冬季污泥堆肥过程温室气体排放特征

污泥堆肥处理是一种简便高效的污泥稳定化技术,但堆肥过程产生的温室气体也引起了国内外的广泛关注,我国关于污泥堆肥,特别是低温环境下的堆肥温室气体排放特征研究和基础数据还很缺乏.本实验采用城市脱水污泥,考察低温环境条件下不同调理剂混合污泥堆肥过程中温室气体的排放特征.结果表明,低温环境条件下污泥堆肥能够顺利进行,但高温期持续时间相对较短而腐熟期温度降低过快.木屑处理的总氮损失低于秸秆处理,然而温室气体总排放当量却高于秸秆处理,木屑和秸秆处理总的CO2排放当量(以干污泥计)分别为169.45 kg·t~(-1)、133.13 kg·t~(-1).木屑与秸秆CH_4累积排放量(以干污泥计)分别为0.648 kg·t~(-1)、0.689 kg·t~(-1),N_2O累积排放量(以干污泥计)分别为0.486 kg·t~(-1)、0.365 kg·t~(-1).CH_4的排放75%以上集中在堆肥前2周,而N_2O则90%以上出现在后腐熟期.整体而言,冬季堆肥高温期持续时间相对较短而腐熟期温度低,出现CH_4排放量相对较低而N_2O较高的现象,CH_4排放量均低于IPCC推荐值,N_2O则均高于IPCC推荐值.因此针对低温环境堆肥工艺,温室气体的减排应重点关注堆肥后期N_2O排放的降低策略.     

Greenhouse gas mitigation and offset options for suckler cow farms: an economic comparison for the Swiss case

We assessed the economic suitability of 4 greenhouse gas (GHG) mitigation options and one GHG offset option for an improvement of the GHG balance of a representative Swiss suckler cow farm housing 35 Livestock units and cultivating 25 ha grassland. GHG emissions per kilogram meat in the economic optimum differ between the production systems and range from 18 to 21.9 kg CO₂-eq./kg meat. Only GHG offset by agroforestry systems showed the potential to significantly reduce these emissions. Depending on the production system agroforestry systems could reduce net GHG emissions by 66% to 7.3 kg CO₂-eq./kg meat in the most intensive system and by 100% in the most extensive system. In this calculation a carbon sequestration rate of 8 t CO₂/ha/year was assumed. The potential of a combination of the addition of lipids to the diet, a cover of the slurry tank and the application of nitrification inhibitors only had the potential to reduce GHG emissions by 12% thereby marginal abatement costs are increasing much faster than for agroforestry systems. A reduction of the GHG emissions to 7.5 kg CO₂-eq./kg meat—possible with agroforestry only—raised costs between 0.03 CHF/kg meat and 0.38 CHF/kg meat depending on the production system and the state of the system before the reduction. If GHG emissions were reduced maximally average costs ranged between 0.37 CHF/kg meat, if agroforestry had the potential to reduce net GHG emissions to 0 kg CO₂-eq., to 1.17 CHF/kg meat if also other options had to be applied.     

不同水分管理方式下水稻生长季N2O排放量估算：模型应用

基于田间原位测定结果,作者建立了不同水分管理方式下稻田N₂O排放估算的统计模型. 在模型验证和输入参数检验的基础上, 本研究应用模型估算了20世纪50～90年代我国稻田水稻生长季N₂O直接排放量. 结果表明, 由于水稻种植面积和氮输入量的增加、以及水分管理方式的变化, 稻田N₂O-N季节排放量从20世纪50年代平均每年9.55 Gg增加到了90年代每年32.26 Gg, 同期伴随着水稻单产的增加. 在20世纪50～90年代间, 我国水稻生产的N₂O-N排放量以平均每10 a6.74 Gg的速度递增. 20世纪50年代和90年代稻田N₂O-N季节排放通量平均分别为0.32 kg·hm^-2和1.00 kg·hm^-2, 相当于季节氮输入总量的0.37%和0.46%. 本研究模型估算50～90年代间稻田N₂O季节排放量的不确定性为59.8%～37.5%. 就全国稻田的不同种植区域而言, 长江中下游地区稻田水稻生长季N₂O排放量占全国稻田N₂O排放总量的51%～56%. 20世纪90年代水稻生长季N₂O排放量约占我国农田N₂O年总排放量的8%～11%. 相对于旱地作物而言, 过去几十年水稻生产的发展在很大程度上减缓了我国农业生产的N₂O排放. 然而, 随着水稻生产中节水灌溉的推广和氮肥施用量的增加, 我国稻田N₂O季节排放量预计将相应增加.     

内蒙古农牧交错带土地利用变化对作物生长季N_2O排放量的影响

在内蒙古农牧交错带,选择4个邻近、不同开垦年限(5、10和50 a)的农田,分别记为C5、C10和C50,以及天然草地作为研究样地;利用静态箱法,在2008—2010年作物生长季(4—10月)进行野外原位试验,研究了土地利用变化对N2O排放量的影响.结果表明:草地与C5、C10、C50农田土壤的N2O排放量在2008—2010年作物生长季均存在显著差异,F分别为53.8、17.3和153.0(P均小于0.001),草地N2O排放量分别为87.6、91.8和211.0 mg/m2.在2008—2010年作物生长季,C5和C10农田土壤N2O排放量比草地低10%~50%;随着开垦年限的增加,N2O累积排放量增加,C50在作物生长季的N2O排放量比草地高10%~30%.草地和不同开垦年限的农田土壤在作物生长季内N2O排放量的58.1%受土壤w(NH4+-N)和含水量的综合影响(R2=0.58,P0.01).     

Cover crop effects on nitrous oxide emission from a manure-treated Mollisol

Agriculture contributes 40–60% of the total annual N₂O emissions to the atmosphere. Development of management practices to reduce these emissions would have a significant impact on greenhouse gas levels. Non-leguminous cover crops are efficient scavengers of residual soil NO₃, thereby reducing leaching losses. However, the effect of a grass cover crop on N₂O emissions from soil receiving liquid swine manure has not been evaluated. This study investigated: (i) the temporal patterns of N₂O emissions following addition of swine manure slurry in a laboratory setting under fluctuating soil moisture regimes; (ii) assessed the potential of a rye (Secale cereale L.) cover crop to decrease N₂O emissions under these conditions; and (iii) quantified field N₂O emissions in response to either spring applied urea ammonium nitrate (UAN) or different rates of fall-applied liquid swine manure, in the presence or absence of a rye/oat winter cover crop. Laboratory experiments investigating cover crop effects N₂O emissions were performed in a controlled environment chamber programmed for a 14 h light period, 18 °C day temperature, and 15 °C night temperature. Treatments with or without a living rye cover crop were treated with either: (i) no manure; (ii) a phosphorus-based manure application rate (low manure): or (iii) a nitrogen-based manure application rate (high manure). We observed a significant reduction in N₂O emissions in the presence of the rye cover crop. Field experiments were performed on a fine-loamy soil in Central Iowa from October 12, 2005 to October 2, 2006. We observed no significant effect of the cover crop on cumulative N₂O emissions in the field. The primary factor influencing N₂O emission was N application rate, regardless of form or timing. The response of N₂O emission to N additions was non-linear, with progressively more N₂O emitted with increasing N application. These results indicate that while cover crops have the potential to reduce N₂O emissions, N application rate may be the overriding factor.     

长期定位有机物料还田对关中平原冬小麦-玉米轮作土壤N2O排放的影响

为定量研究有机物料还田对农田土壤N2O排放的影响,采用静态暗箱-气相色谱法对关中平原冬小麦-玉米轮作24 a长期定位施肥试验地土壤N2O排放速率和相关环境因子进行了周年观测,试验处理为对照(CK,0 kg·hm~(-2))、氮磷钾(NPK,353kg·hm~(-2))、氮磷钾加秸秆还田[NPKS,(353+40)kg·hm~(-2)]和氮磷钾加牛粪[NPKM,(238+115)kg·hm~(-2)]4个处理.结果表明观测期内,CK处理N2O排放速率较小[2.9 g·(hm~2·d)~(-1)];施肥处理在冬小麦季施肥和玉米季灌溉后均出现排放峰,最高值分别为NPKS[113.4 g·(hm~2·d)~(-1)]和NPKM[495.0 g·(hm~2·d)~(-1)]处理.各处理N2O排放通量与土壤湿度均呈显著正相关关系(r0.28,P0.05).CK、NPK、NPKS和NPKM处理N2O年排放总量分别为(0.1±0.0)、(2.6±0.1)、(3.4±0.7)和(2.9±0.3)kg·hm~(-2),施肥处理排放总量显著高于CK处理(P0.05),但施肥处理之间差异不显著(P=0.06),说明施肥促进了N2O排放,但有机物料还田未能显著增加N2O排放.各施肥处理N2O直接排放系数分别为0.72%、0.83%和0.80%,均低于IPCC缺省值1%.施肥处理中,NPKM处理的单位产量N2O排放量最低.