土壤水分状况对CH4氧化,N2O和CO2排放的影响

实验室培育试验表明，土壤氧化ＣＨ４，排放Ｎ２Ｏ和ＣＯ２的最佳水分含不量。水稻土氧化ＣＨ４的最佳水分含同于半干旱草地土壤，均接近于土壤环境常年水分含量。水稻土Ｎ２Ｏ排放量随着水分含量的下降而增加，半干旱草地土壤则随着水分含量的下降而减少，表明背离土壤环境上水分含量越远，Ｎ２Ｏ的排放量越大。因而，ＣＨ４氧化和Ｎ２Ｏ排放对土壤水分含量的反应呈极显著的负相关性。ＣＯ２排放的最佳水分含量接近或高于ＣＨ４氧化     

不同灌溉模式和施氮处理下稻田 CH4 和 N2O 排放

【目的】研究不同灌溉模式和施氮处理稻田 CH₄ 和 N₂O 的排放规律、综合增温潜势和综合排放强度,以期获得降低稻田 CH₄ 和 N₂O 排放的灌溉模式和施氮管理。【方法】2015～2016 年在广西南宁市灌溉试验站进行晚稻和早稻大田试验,两次试验均设 3 种灌溉模式:常规灌溉 (CIR)、“薄浅湿晒 ”灌溉 (TIR) 和干湿交替灌溉 (DIR)。 2 种尿素-N 和猪粪-N 比例:100% 尿素-N (FM1),50% 尿素-N + 50% 猪粪-N (FM2)。共设 CIR-FM1、TIR-FM1、DIR-FM1、CIR-FM2、TIR-FM2 和 DIR-FM2 6 个处理,用静态箱–气相色谱法测定了水稻生育期内稻田 CH₄ 和 N₂O 排放通量,分析了早晚稻生育期内 CH₄ 和 N₂O 累积排放量和综合增温潜势,并结合产量分析了 CH₄ 和 N₂O 综合排放强度。【结果】DIR 下 FM2 处理早稻产量和两季总产量比 FM1 处理分别提高 18.8% 和 17.7%,FM2 下 TIR 和 DIR 模式早稻产量分别比 CIR 模式提高 20.9% 和 37.4% 以及 DIR 模式两季总产量比 CIR 模式提高 21.5%。不同处理早晚稻生育前期 CH₄ 排放通量较高,生育中后期 CH₄ 排放通量较低。水稻生育期内 TIR 和 DIR 模式 CH₄ 累积排放量低于 CIR 模式,FM1 处理 CH₄ 累积排放量低于 FM2 处理。不同处理早晚稻生育前期 N₂O 的排放通量为负值或者较低,N₂O 排放主要集中在晒田完成复水之后及成熟期稻田水分落干时,DIR 模式 N₂O 累积排放量显著高于 CIR 模式,FM2 处理 N₂O 累积排放量高于 FM1 处理。不同处理稻田 CH₄ 和 N₂O 的排放彼此间存在消长关系。CH₄ 对综合增温潜势的贡献率达 99% 以上,而 N₂O 的贡献率不足 1%。3 种灌溉模式下 FM1 处理 CH₄ 或 N₂O 增温潜势、CH₄ 和 N₂O 综合增温潜势和排放强度均低于 FM2 处理,2 种施氮处理下 TIR 和 DIR 模式 CH₄ 和 N₂O 综合增温潜势和排放强度低于 CIR 模式。【结论】与常规灌溉相比,“薄浅湿晒”灌溉水稻产量和 N₂O 排放有所提高,但是降低 CH₄ 排放量及 CH₄ 和 N₂O 综合增温潜势和排放强度;干湿交替灌溉增加水稻产量和 N₂O 排放,但是降低 CH₄ 的排放量及 CH₄ 和 N₂O 综合增温潜势和排放强度,因此,“薄浅湿晒”和干湿交替灌溉模式是有效降低稻田 CH₄ 和 N₂O 综合增温潜势和排放强度的两种灌溉模式。在这两种灌溉方式下,与猪粪尿素配施相比,单施尿素显著降低 CH₄ 和 N₂O 综合增温潜势和排放强度。     

稻田CH4和N2O排放对大气CO2浓度升高响应的研究进展

大气CO₂浓度升高是全球气候变化的主要驱动力,可直接或间接影响陆地生态系统碳氮循环。阐明稻田生态系统CH₄和N₂O排放对大气CO₂浓度升高的响应及其机制,是农业生产应对全球气候变化的重要组成部分。本文综述了国内外不同大气CO₂浓度升高模拟技术平台条件下稻田CH₄和N₂O排放的响应规律,进一步讨论分析了大气CO₂浓度升高影响CH₄和N₂O排放的相关机制,并展望了今后稻田CH₄和N₂O排放对大气CO₂浓度升高响应的主要研究方向,以期为应对全球气候变化提供理论依据和技术支撑。     

旱作及水作条件下稻田CH4和N2O排放的观察研究

通过田间试验研究不同土表覆盖处理旱作和水作水稻全生育期内土壤微量气体的排放。结果表明 ,旱作稻田当季N2 O的排放总量是水作稻田的 5～ 6倍 ,而水作稻田CH4 的排放总量是旱作稻田的8～ 1 9倍。不同覆盖旱作处理N2 O的排放总量为 :裸露 >覆膜 >盖草 ,CH4 排放总量为 :覆膜 >裸露 >盖草。水作稻田CH4 的排放与水稻生育期关系密切 ,以分蘖盛期的 5 0mgm- 2 h- 1为最大。旱作稻田N2 O的排放与施氮关系密切 ,其排放通量峰值出现的时间因施氮时期不同而异 ,基肥的峰值 (2 1 1 6 7μgm- 2 h- 1)出现在施肥后第 1 1d ;分蘖肥的峰值 (4 3 94 3 μgm- 2 h- 1)出现在施肥后第 9～ 1 0d ;穗肥的峰值则在施肥后的第 6d出现 ,达 3 3 3 5 0 μgm- 2 h- 1。     

添加秸秆及其生物质炭对淹水条件下砖红壤N2O和CH4排放的影响

为探讨添加秸秆及其生物质炭对淹水条件下砖红壤N₂O和CH₄排放的影响,以海南砖红壤为供试土壤,设置了玉米秸秆（Straw）、生物质炭（Biochar）、秸秆 + 生物质炭（Mix）和对照（CK）4个处理,探讨了等秸秆用量条件下添加不同秸秆形态对土壤氧化亚氮（N₂O）和甲烷（CH₄）排放的影响及形成强还原环境的可行性。结果表明:与CK处理相比,三个处理均可显著降低土壤N₂O累计排放量,但仅Straw处理可显著促进土壤CH₄排放、其它两个处理对土壤CH₄排放影响不显著,致使straw处理综合温室效应增加明显。与CK处理相比,与Mix处理5天内土壤氧化还原电位（Eh）显著下降,而Biochar处理土壤Eh变化不显著;三个处理均使土壤pH上升、但Straw与Biochar处理之间差异不显著,Mix处理土壤有机碳、全氮及速效钾含量显著增加。因此,玉米秸秆及其生物质炭的配合施用,既可有效降低淹水条件下海南砖红壤排放CH₄和N₂O的综合温室效应,还能改善土壤养分状况但易于形成强还原条件。     

稻鸭共作对不同栽培环境稻季CH4和N2O排放的影响

稻田是大气温室气体甲烷(CH₄)和氧化亚氮(N₂O)的重要排放源, 稻田温室气体减排一直是生态农业研究的热点。目前, 采用水稻品种选择利用、水分控制管理、肥料运筹管理、耕作制度调整以及种养结合模式等方法来减少稻田温室气体排放有较好实践效应, 但不同稻田栽培环境(露地、网室)基础上的稻鸭共作对麦秸全量还田的稻田温室气体排放特征及相关土壤理化特性关联性的影响尚为少见。本研究采用裂区设计, 在两种栽培环境条件下, 以无鸭子放养的常规稻作和麦秸不还田为对照, 在等养分条件下分析麦秸全量还田与稻鸭共作模式对稻田土壤氧化还原电位、CH₄排放量、产CH₄潜力及CH₄氧化能力、N₂O排放量及N₂O排放高峰期土壤反硝化酶活性、全球增温潜势、水稻产量的影响, 为稻田可持续生产和温室气体减排提供参考。结果表明, 麦秆还田增加了稻田产CH₄潜力、提高了CH₄排放量, 降低了稻田土壤反硝化酶活性、土壤氧化还原电位和N₂O排放量, 整体上导致全球增温潜势上升96.89%~123.02%; 稻鸭共作模式, 由于鸭子的不间断活动提高了稻田土壤氧化还原电位, 降低了稻田产CH₄潜力, 增强了稻田CH₄氧化能力, 从而降低稻田CH₄排放量, N₂O排放量虽有提高, 整体上稻鸭共作模式的全球增温潜势较无鸭常规稻田下降8.72%~14.18%; 网室栽培模式显著提高了稻田土壤氧化还原电位, 降低稻田产CH₄潜力、CH₄氧化能力和土壤反硝化酶活性, 减少了稻田CH₄和N₂O排放量, 全球增温潜势降低6.35%~13.14%。本试验条件下, 稻田土壤的CH₄氧化能力是产CH₄潜力的2.21~3.81倍; 相同环境条件下, 稻鸭共作和麦秸还田均能增加水稻实际产量, 网室栽培的所有处理较相应的露地栽培减少了水稻实际产量1.19%~5.48%。本试验表明, 稻鸭共作和网室栽培可减缓全球增温潜势, 稻鸭共作和麦秸还田能够增加水稻实际产量。     

黑麦草鲜草翻压还田对双季稻CH4与N2O排放的影响

为了研究黑麦草鲜草翻压还田对稻田温室气体排放的影响,该文利用静态箱-盆栽装置观测了尿素、黑麦草鲜草翻压还田、半量尿素与半量黑麦草鲜草混施和对照4个处理稻田CH4和N2O排放.结果表明:黑麦草鲜草翻压还田、半量尿素与半量黑麦草鲜草混施的CH4排放通量分别比对照增加了371％和210％,比尿素增加了152％和66％:尿素的CH4排放比对照高87％,差异均达到显著水平(P＜0.05).黑麦草鲜草翻压还田的CH4排放在3个时期(早稻移栽前,早稻生长期和晚稻生长期)分布均匀,约60％的CH4排放于早稻移栽前和早稻生长期.尿素的N2O排放分别为黑麦草鲜草翻压还田、半量尿素与半量黑麦草鲜草混施和对照的18倍、6.6倍和25倍.CH4和N2O的全球增温潜势(GWP)依次为黑麦草鲜草翻压还田＞半量尿素与半量黑麦草鲜草混施＞尿素＞对照,差异均显著(P＜0.05).黑麦草鲜草翻压还田虽然增加了稻田CH4排放,但减少了N2O排放,抑制了 尿素对N2O的排放.     

西北干旱区两种不同栽培管理措施下棉田CH4和N2O排放通量研究

采用静态箱-气相色谱法对西北干旱区当前普遍采用的膜下滴灌和传统的无膜漫灌两种栽培管理下土壤CH4和N2O通量日变化和季节变化特征进行了研究。结果表明,随时间的推移,无膜漫灌栽培管理措施下棉田土壤CH4日变化通量呈先降后升趋势,而膜下滴灌栽培处理CH4排放通量日变化则呈现先升后降趋势;在整个生长季节,无膜漫灌和膜下滴灌土壤CH4季节变化规律不太明显,前者吸收大气CH4 45.2～52.5 mg m-2 a-1,后者释放CH4通量为0.7～23.1 mg m-2 a-1。两种栽培管理措施下棉田土壤N2O通量的日变化和季节变化均随时间的推移均呈现先升后降趋势,但是,无膜漫灌日均排放N2O通量显著高于膜下滴灌。在整个生长季节,无膜漫灌土壤N2O释放量(N2O 99.3～320.0 mg m-2 a-1)显著高于膜下滴灌(N2O60.0～259.0 mg m-2 a-1)。以上结果说明,膜下滴灌栽培管理措施可以改变旱田传统无膜漫灌栽培土壤与大气CH4的交换方向,促进土壤CH4向大气的排放,但对N2O通量日变化和季节变化规律不产生影响,显著降低土壤N2O的排放量。     

耕作措施对双季稻田CH4与N2O排放的影响

随着全球气温的不断升高,温室气体减排成为研究的热点。该文旨在研究不同耕作措施下双季稻田CH4及N2O排放特征及其消长关系,为稻田温室气体减排及土壤固碳潜力评价提供依据。试验在湖南省宁乡县进行,通过静态箱法测定翻耕秸秆还田（CT）、旋耕秸秆还田（RT）、免耕秸秆还田（NT）的稻田CH4及N2O排放。结果表明：CH4排放主要来自于晚稻田,翻耕、旋耕和免耕晚稻田CH4排放分别占研究时段CH4排放的69%,67%,73%;各处理冬闲季CH4排放均不到研究时段排放量1%,冬闲CH4排放量为RT＞CT＞NT,差异显著;N2O排放时间变异性较大,早稻稻田N2O排放量为RT＞NT＞CT,晚稻稻田N2O排放量为NT＞RT＞CT,冬闲期各处理稻田N2O均为负排放;从研究时段排放量分析,翻耕秸秆还田有利于减少N2O排放,免耕秸秆还田有利于减少CH4排放;CH4与N2O排放呈显著负相关,冬闲季稻田CH4与N2O排放相关性不显著。总之,NT减少了CH4排放,虽N2O排放略有增加,但CH4与N2O引发的综合温室效应有所减弱。     

氮肥品种对亚热带土壤N2O排放的影响

以亚热带湿热地区红壤性旱地(SU),灌丛(GB),林地(QF)为研究对象,通过在30℃和60%WHC水分条件下,35 d的培养试验,研究了外源铵态氮输入对土壤N2O排放的影响。结果表明,对于pH较高的土壤SU(pH=6.27),施用硫铵、尿素和碳酸氢铵后,硝态氮累积量和N2O排放量均高于未施氮的处理,且随施N量增加而增加。对于酸性土壤GB(pH=4.82)和QF(pH=4.46),施用硫铵明显地抑制硝化作用,但却极大地促进N2O排放;施用尿素和碳酸氢铵对硝化作用有微弱的促进作用或无明显的影响,N2O的排放则略低于对照或无明显差异。酸性土壤中,加入不同类型的氮肥后,N2O排放量与硝态氮含量的比例与加入氮肥后测定的土壤pH具有显著的负相关关系。氮肥品种影响N2O排放量与硝态氮产生量比例的机理值得进一步研究。     

浮萍对福州平原稻田CH4和N2O排放的影响分析

浮萍是稻田中常见的漂浮在水面的水生植物,具有固氮作用,但是,浮萍对稻田温室气体排放的影响尚不明确.以位于湿润亚热带的福州平原稻田为研究对象,探讨浮萍对该区域稻田CH4和N2O排放的影响,为科学评价、准确编制我国水稻田温室气体排放清单提供基础数据.研究结果表明,观测期内,有萍小区和无萍小区CH4排放范围分别为0.19～26.50 mg·m-2·h-1和1.02～28.02 mg·m-2·h-1,平均值分别为9.28 mg·m-2·h-1和11.66 mg·m-2·h-1,有萍小区CH4排放低于无萍小区(P＜0.01),有萍小区CH4排放高峰比无萍小区约提前1周,高峰期后排放迅速降低;有萍小区和无萍小区N2O排放范围分别为-50.11～201.82 μg·m-2·h-1和-28.93～54.42μg·m-2·h-1,平均值分别为40.29 μg·m-2·h-1和11.93 μg·m-2·h-1,有萍小区N2O排放高于无萍小区(P＜0.05).稻田排干后,N2O排放迅速上升,2个小区N2O排放呈现出相似的规律.有萍小区和无萍小区的CH4与N2O排放的影响因子有所不同.综合考虑CH4和N2O两种温室气体,CH4仍是稻田温室效应产生的主要贡献者,浮萍可降低位于沿海区域的福州平原稻田综合温室效应的17.3％.     

Wheat straw management affects CH4 and N2O emissions from rice fields

A 3-year field experiment was conducted in Jiangsu Province, China from 2004 to 2006 to investigate CH₄ and N₂O emissions from paddy fields as affected by various wheat straw management practices prior to rice cultivation. Five methods of returning wheat straw, no straw, evenly incorporating, burying straw, ditch mulching and strip mulching, were adopted in the experiment. Evenly incorporating is the most common management practice in the region. Results showed that compared with no straw, evenly incorporating increased CH₄ emission significantly by a factor of 3.9-10.5, while decreasing N₂O emission by 1-78%. Methane emission from burying straw was comparable with that from evenly incorporating, while N₂O emission from burying straw was 94-314% of that from evenly incorporating. Compared with evenly incorporating, CH₄ emission was decreased by 23-32% in ditch mulching and by 32% in strip mulching, while N₂O emission was increased by a factor of 1.4-3.7 in ditch mulching and by a factor of 5.1 in strip mulching. During the rice-growing season, the emitted N₂O was negligible compared to that of emitted CH₄. No significant difference in grain yield was observed between ditch mulching, burying straw, evenly incorporating and no straw. Compared with no straw, the grain yield was increased by 27% in strip mulching. Based on these results, the best management practice for returning wheat straw to the soil is strip mulching wheat straw partially or completely onto the field surface, as the method reduced CH₄ emission from rice fields with no decrease in rice yield.     

氢醌、双氰胺组合影响稻田甲烷和氧化亚氮排放研究进展

稻田是大气中CH4和N2O的重要来源。大量氮肥的施入不仅影响稻田CH4和N2O排放,且易造成NH3挥发、NO2-和NO3-淋溶及N2O、N2等形式的氮损失。脲酶抑制剂和硝化抑制剂通过缓解尿素水解及抑制硝化反硝化反应减少稻田N2O排放量,但对稻田CH4产生排放的影响报道不一。脲酶抑制剂氢醌(HQ)和硝化抑制剂双氰胺(DCD)是近年来研究较多的组合。本文试图在前人研究的基础上,综述HQ和DCD的基本性质及作用机理,总结HQ/DCD组合在稻田生态系统的应用状况、使用效果及存在问题,并特别讨论了HQ/DCD施用对稻田CH4排放的影响机理,旨在为合理使用脲酶/硝化抑制剂、有效减缓稻田温室气体排放和提高氮肥利用率等方面提供理论依据。     

稻草生物炭对干湿交替稻田CH4和N2O排放的影响

为探究稻草生物炭和灌溉方式对稻田CH₄和N₂O排放的影响,揭示生物炭在干湿交替稻田中的应用潜力,该研究采用大田裂区试验,设置常规淹灌（I_CF）和干湿交替灌溉（I_AWD）2种灌溉方式,不施生物炭（B₀）和施20 t/hm²生物炭（B₂₀）2种施炭水平,连续3 a对稻田CH₄、N₂O排放和水稻产量进行了观测研究。结果表明：与I_CF相比,I_AWD在显著降低CH₄排放（63.03%～78.89%）的同时也促进了N₂O排放（100%～122.67%）。生物炭施加首年对CH₄排放无显著影响,但第2年和第3年分别显著减少CH₄排放21.99%和38.21%;而对N₂O排放3 a均起到抑制作用,降幅达28.26%～33.10%。生物炭3 a平均增加土壤有机碳27.03%。施生物炭第1年水稻略有减产,但第2和第3年表现为正效应。主要是由于初期秸秆生物炭碱性较大,表现出了明显的石灰效应;但随着pH值逐步恢复正常后,生物炭固碳减排和缓释增效特性逐渐显现。尤其在2021年,B₂₀较B₀增产11.02%,显著降低37.50%的全球增温潜势（global warming potential,GWP）和42.86%的温室气体排放强度（greenhouse gas intensity,GHGI）;同时,在B₀条件下,I_AWD较I_CF增加137.21%的N₂O排放,但B₂₀条件下降低I_AWD处理32.52%的N₂O排放,有效抑制I_AWD对N₂O排放增加的负面效应。整体来看,与I_CFB₀处理相比,I_AWDB₂₀处理显著降低CH₄排放,降幅为83.78%,同时降低77.98%的GWP和78.95%的GHGI。该研究为揭示生物炭固碳减排的正效应及其在稻田生态系统中的应用潜力,同时全面探究其对稻田增产、CH₄和N₂O排放的年限影响,为缓解实际稻田生产过程中CH₄和N₂O的排放,实现稻田绿色、高效、可持续生产提供理论依据。     

秸秆条带状覆盖对稻田CH_4和N_2O排放的影响

采用3种秸秆还田方式(对照、秸秆均匀混施和秸秆条带状覆盖)进行田间试验,观测稻田CH4和N2O的排放通量,以探讨秸秆条带状覆盖对稻田CH4和N2O排放的影响。结果表明:秸秆条带状覆盖的CH4排放量是对照的2.7倍,二者的N2O排放量无明显差异;秸秆条带状覆盖的稻田CH4排放量较秸秆均匀混施减少32%,其N2O排放量是后者的5.1倍;稻田排放CH4和N2O的全球增温潜势(GWP)为:秸秆均匀混施秸秆条带状覆盖对照,且差异显著;秸秆条带状覆盖的水稻产量分别较对照和秸秆均匀混施增加27%和17%。秸秆条带状覆盖是值得推荐的稻季秸秆还田方式。     

CH4 oxidation and emissions of CH4 and N2O from Lolium perenne swards under elevated atmospheric CO2

Emissions of N₂O and CH₄ and CH₄ oxidation rates were measured from Lolium perenne swards in a short-term study under ambient (36 Pa) and elevated (60 Pa) atmospheric CO₂ at the Free Air Carbon dioxide Enrichment experiment, Eschikon, Switzerland. Elevated pCO₂ increased (P<0.05) N₂O emissions from high N fertilised (11.2 g N m⁻²) swards by 69%, but had no significant effect on net emissions of CH₄. Application of ¹³C-CH₄ (11 μl l⁻¹; 11 at.% excess ¹³C) to closed chamber headspaces in microplots enabled determination of rates of ¹³C-CH₄ oxidation even when net CH₄ fluxes from main plots were positive. We found a significant interaction between fertiliser application rate and atmospheric pCO₂ on ¹³C-CH₄ oxidation rates that was attributed to differences in gross nitrification rates and C and N availability. CH₄ oxidation was slower and thought to be temporarily inhibited in the high N ambient pCO₂ sward. The most rapid CH₄ oxidation of 14.6 μg ¹³C-CH₄ m⁻² h⁻¹ was measured in the high fertilised elevated pCO₂ sward, and we concluded that either elevated pCO₂ had a stimulatory effect on CH₄ oxidation or inhibition of oxidation following fertiliser application was lowered under elevated pCO₂. Application of ¹⁴NH₄¹⁵NO₃ and ¹⁵NH₄¹⁵NO₃ (10 at.% excess ¹⁵N) to different replicates enabled determination of the respective contributions of nitrification and denitrification to N₂O emissions. Inhibition of CH₄ oxidation in the high fertilised ambient pCO₂ sward, due to competition between NH₃ and CH₄ for methane monooxygenase enzymes or toxic effects of NH₂OH or NO₂⁻ produced during nitrification, was hypothesised to increase gross nitrification (12.0 mg N kg dry soil⁻¹) and N₂O emissions during nitrification (327 mg ¹⁵N-N₂O m⁻² over 11 d). Our results indicate that increasing atmospheric concentrations of CO₂ may increase emissions of N₂O by denitrification, lower nitrification rates and either increase or decrease the ability of soil to act as a sink for atmospheric CH₄ depending on fertiliser management.     

CH4 oxidation and N2O emissions at varied soil water-filled pore spaces and headspace CH4 concentrations

Emission of N₂O and CH₄ oxidation rates were measured from soils of contrasting (30-75%) water-filled pore space (WFPS). Oxidation rates of ¹³C-CH₄ were determined after application of 10 μl ¹³C-CH₄ l⁻¹ (10 at. % excess ¹³C) to soil headspace and comparisons made with estimates from changes in net CH₄ emission in these treatments and under ambient CH₄ where no ¹³C-CH₄ had been applied. We found a significant effect of soil WFPS on ¹³C-CH₄ oxidation rates and evidence for oxidation of 2.2 μg ¹³C-CH₄ d⁻¹ occurring in the 75% WFPS soil, which may have been either aerobic oxidation occurring in aerobic microsites in this soil or anaerobic CH₄ oxidation. The lowest ¹³C-CH₄ oxidation rate was measured in the 30% WFPS soil and was attributed to inhibition of methanotroph activity in this dry soil. However, oxidation was lowest in the wetter soils when estimated from changes in concentration of ¹²⁺¹³C-CH₄. Thus, both methanogenesis and CH₄ oxidation may have been occurring simultaneously in these wet soils, indicating the advantage of using a stable isotope approach to determine oxidation rates. Application of ¹³C-CH₄ at 10 μl ¹³C-CH₄ l⁻¹ resulted in more rapid oxidation than under ambient CH₄ conditions, suggesting CH₄ oxidation in this soil was substrate limited, particularly in the wetter soils. Application of and (80 mg N kg soil⁻¹; 9.9 at.% excess ¹⁵N) to different replicates enabled determination of the respective contributions of nitrification and denitrification to N₂O emissions. The highest N₂O emission (119 μg ¹⁴⁺¹⁵N-N₂O kg soil⁻¹ over 72 h) was measured from the 75% WFPS soil and was mostly produced during denitrification (18.1 μg ¹⁵N-N₂O kg soil⁻¹; 90% of ¹⁵N-N₂O from this treatment). Strong negative correlations between ¹⁴⁺¹⁵N-N₂O emissions, denitrified ¹⁵N-N₂O emissions and ¹³C-CH₄ concentrations (r=−0.93 to −0.95, N₂O; r=−0.87 to −0.95, denitrified ¹⁵N-N₂O; P<0.05) suggest a close relationship between CH₄ oxidation and denitrification in our soil, the nature of which requires further investigation.     

Elevated atmospheric CO2 reduces CH4 and N2O emissions under two contrasting rice cultivars from a subtropical paddy field in China

Elevated CO₂(eCO₂) and rice cultivars can strongly alter CH₄ and N₂ O emissions from paddy fields.However,detailed information on how their interaction affects greenhouse gas fluxes in the field is still lacking.In this study,we investigated CH4 and N₂ O emissions and rice growth under two contrasting rice cultivars(the strongly and weakly responsive cultivars) in response to eCO₂,200 μmol mol^-1 higher than the ambient ...     

不同时期施用生物炭对稻田N_2O和CH_4排放的影响

通过分别在水稻季(R)和小麦季(W)设置对照(RB0-N0、WB0-N0)、单施氮肥(RB0-N1、WB0-N1)、20 t hm-2生物炭与氮配施(RB1-N1、WB1-N1)、40 t hm-2生物炭与氮配施(RB2-N1、WB2-N1)等8个处理,研究稻麦轮作周年系统N2O和CH4排放规律及其引起的综合温室效应(Global warming potential,GWP)和温室气体强度(Greenhouse gas intensity,GHGI)特征。结果表明:稻季配施20 t hm-2生物炭对N2O和CH4的排放、作物产量及GWP和GHGI均都无明显影响;稻季配施40 t hm-2生物炭能显著降低8.6%的CH4的排放和9.3%的GWP,显著增加作物产量17.2%。麦季配施20 t hm-2生物炭虽然对温室气体及GWP影响不明显,但显著增加21.6%的作物产量,从而显著降低21.7%的GHGI;麦季配施40 t hm-2生物炭能显著降低20.9%和11.3%的N2O和CH4排放,显著降低15.7%和23.5%的GWP和GHGI。因此麦季配施生物炭对减少N2O和CH4的排放、增加稻麦轮作产量及降低GWP和GHGI的效果较稻季配施生物炭效果更好。