晚稻期间秸秆还田对早稻田CH_4和N_2O排放以及产量的影响

选取湖南双季稻田为研究对象,采用静态箱-气相色谱法对晚稻期间秸秆还田配施减量化肥(DNPK+RS)和施化肥(NPK)处理下后季早稻田(2009年)的CH4和N2O排放通量进行观测。结果表明,在早稻田等量化肥条件下,DNPK+RS比NPK增加早稻田CH4排放的81%,减少N2O排放的53%。早稻产量表明,DNPK+RS显著低于NPK(P<0.05)。晚稻期间以秸秆还田来代替部分化肥,会降低次年早稻的有效穗数和肥料增产效应。DNPK+RS处理的单位产量的全球增温潜势为NPK的2倍。秸秆还田应该重视与化肥的搭配比例,否则会降低水稻产量,同时增加下季早稻的温室效应。     

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。     

稻田CH4和N2O综合排放对控制灌溉的响应

为了揭示水稻控制灌溉对稻田CH4和N2O综合排放的影响,该文采用静态暗箱-气相色谱法对控制灌溉稻田CH4和N2O排放进行原位观测,分析稻田CH4和N2O综合排放对控制灌溉水分调控的动态响应。结果表明,控制灌溉稻田CH4排放通量多低于常规灌溉稻田,且主要集中在水稻分蘖前期,峰值出现在土壤脱水后第1～2d,排放总量较常规灌溉稻田减少81.2%～82.8%;N2O排放通量多高于常规灌溉稻田,峰值出现在肥后且土壤脱水后3～4d,排放总量较常规灌溉稻田增加了121.8%～144.3%。控制灌溉稻田CH4和N2O的综合全球增温潜势较常规灌溉稻田显著减少(p<0.05),减少幅度为15.0%～34.8%。控制灌溉显著降低了稻田CH4和N2O的综合温室效应。     

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。     

添加生物炭对华南早稻田CH4和N2O排放的影响

通过田间试验,采用静态箱-气象色谱法研究生物炭添加对华南早稻田甲烷(CH4)和氧化亚氮(N2O)排放的影响.试验设对照(CK),BC1、BC2、BC3(土壤中分别混入5、10、20t·hm-2生物炭)、RS(稻草直接还田)和RI(稻草加腐熟剂还田)6个处理.结果表明,与CK、RS和RI相比,生物炭处理能降低稻田CH4和N2O排放量及排放强度,综合排放强度最低的为BC3处理,值为0.98 kgCO2-eq· kg-1.在本实验的处理范围内,生物炭添加量越高,CH4平均排放通量及其季节排放总量越低,最低值分别为22.11mg·m-2·h-1和93.21kg·hm-2;N2O排放通量和季节排放总量则随生物炭添加量的增加呈上升趋势,最高值分别为285.65 μg·m-2·h-1和1.07kg·hm-2,但依然小于对照处理(368.13μg·m-2 ·h-1和1.13kg·hm-2).此外,试验发现高用量的生物炭(即BC3)处理水稻产量最高,值为7152.58kg·hm-2.综合分析各处理,BC3对减缓温室效应和稳定水稻生产贡献最大.     

不同秸秆还田模式与氮肥施用量对土壤N2O排放的影响

以山东省桓台县为试验地点，分析在高产条件下，不同秸秆还田模式和氮肥施用量对农田N2O排放的影响。试验结果表明，氮肥施用量与秸秆还田模式都是影响土壤N2O排放的重要因素；小麦秸秆还田可以大大降低土壤N2O的排放，施用有机粪肥是影响N2O排放的另一重要因素。     

冬季秸秆还田对冬灌田水稻生长期CH4产生、氧化和排放的影响

有机肥施用和土壤水分管理是影响稻田CH4排放最重要的2个因素。本文通过室内培养和田间试验研究了冬季秸秆还田对冬灌田水稻生长期CH4的产生、氧化和排放的影响。结果表明:淹水混施处理CH4产生潜力在水稻移栽后35和51天显著大于淹水不施肥处理(p0.05),其余时间则无显著差异(p0.05);冬季秸秆还田对CH4氧化潜力无显著影响(p0.05),水稻生长期土温和稻田施用氮肥可能是较其更重要的影响因素;淹水混施处理CH4平均排放通量(CH426.7mg/(m2·h))显著大于淹水不施处理(CH420.3mg/(m2·h))(p0.05)。     

丘陵区稻田N2O排放的特点

１９９３－１９９４年在中国科学院红壤生态试验站通过田间试验研究了丘陵区稻田Ｎ２Ｏ排放的特点。结果表明,稻田Ｎ２Ｏ排放主要集中在水分落干期间,淹水状态下几乎没有Ｎ２Ｏ排放。由于早稻稻草还田、晚稻稻田Ｎ２Ｏ排放量即使在水分离落干期间也不高。稻田Ｎ２Ｏ排放量随地形降低而逐渐增加,１９９３－１９９４年两年中坡底、坡腰和坡顶稻田水稻生长期平均Ｎ２Ｏ－Ｎ排放通量分别为１０．９０、５．６０和２．１１μｇ／（ｍ＾     

三峡库区农业发展现状及农田CH_4和N_2O排放与减排对策

全球气候变暖的主要原因在于大气中的温室气体含量的急速增加。以低碳为特征的新发展模式成为目前减少温室气体排放、应对全球气候变暖的根本途径。农业生态系统作为最大的人工生态系统,成为温室气体的第二大来源。因此,农业活动与气候变暖关系密切。以三峡库区为例,在分析了库区农业发展面临的问题的基础上,初步估算了库区水田CH4及耕地(含水田和旱地)N2O温室气体的排放量。2008年库区水田CH4及农田N2O的排放量分别为5.5×104~6.5×104 t、8500~10000 t,提出推广免耕等保护性耕作法、改变传统种植模式,合理施肥、改进稻田生产管理技术、对稻田生产系统的时间和空间差异进行管理。     

施肥对稻田N2O排放的影响

肥料施用是影响稻田N20排放的重要因素之一。以国内外相关文献为基础,综述了肥料的种类、施用量、施用方式和施用时间对稻田N2O排放的影响,指出了有待研究的内容：加强对土壤N2O排放机理的研究;进一步研究肥料施用对稻田N2O排放的影响;进一步研究施肥管理措施对稻田温室气体（CH4和N2O）排放的交互影响,寻求科学合理、切实可行的减排措施。     

Emissions of trace gases (CO2, CO,CH4, and N2O) resulting from rice straw burning

Emissions of trace gases (CO₂, CO, CH₄, N₂O) resulting from rice straw burning were measured by using the open chamber method. The carbon contained in rice straw was mainly released to the atmosphere as CO₂. The percentage of CO₂-C emitted in total C in rice straw was in the range of 57–81%, followed by CO-C (5–9%). The percentages of CH₄-C and N₂O-N in total C and N in rice straw were in the range of 0.43–0.90 and 1.16–1.50%, respectively. In the case of the rice straw which had been left in the field for a period of one month after harvest, emission of imperfect combustible gases such as CO and CH₄ during burning increased slightly, while that of perfect combustible gas, CO₂, was reduced. The amount of CH₄ emission from rice straw burning was comparable to that from paddy fields.     

中国东北休闲期稻田温室气体排放

CH4, N2O and CO2 emissions from northeast Chinese rice fields were measured in the fallow season （November to March） to investigate the effects of freezing-thawing on the emissions. Both CH4 emission from and atmospheric CH4 oxidation by the soil occurred, but the flux was small. During the fallow season, rice fields acted as a minor source of atmospheric CH4, which accounted for about 1% of the CH4 emission during the rice growing period. The field was also a substantial source of atmospheric N20, which ranged between 40 to 77 mg m-2 and eu=counted for 40%-50% of the annual N20 emission. The largest N20 flux was observed in the thawing period during the fallow season. Laboratory incubation tests showed that the largest N20 flux came from the release of N20 trapped in frozen soil. Tillage and rice straw application （either mulched on the soil surface or incorporated in the soil） stimulated the CH4 and CO2 emissions during the fallow season, but only straw application stimulated N2O emission substantially.     

Incorporation of rice straw mitigates CH4 and N2O emissions in water saving paddy fields of Central Vietnam

This study evaluated the effects of rice straw and water regimes on CH₄ and N₂O emissions from paddy fields for two rice growing seasons (summer 2014 and spring 2015). Water regimes included alternating wet–dry irrigation (AWD) maintained at three levels (–5 cm, – 10 cm and –15 cm) in comparison to continuous flooding irrigation (CF). Rice straw (5 t ha^–1) was incorporated into the top soil (0 – 15 cm), distributed and burned in situ. Results showed that using burned in situ rice straw was found to reduce seasonal cumulative CH₄ emission (24–34% in summer; 18–28% in spring), N₂O emission (21–32% in summer; 22–29% in spring) and lower rice yield (8–9%) than rice straw incorporation into top soil. AWD methods reduced the amount of CH₄ production (22.6–41.5%) and increased N₂O emission (25–26%) without any decrease in rice yield. Rice straw incorporation into the top soil with AWD had higher water productivity (23–37%) than rice straw when burned in situ with CF. The results conclude that AWD and rice straw management can be employed as mitigation strategy for CH₄ and N₂O emissions from paddy fields in Central Vietnam.     

膨松剂对厨余垃圾堆肥CH4、N2O和NH3排放的影响

厨余垃圾有别于混合生活垃圾,具有高有机质含量和高含水率等特点,单独堆肥会产生大量CH4、N2O、NH3和渗滤液,为减少厨余垃圾堆肥过程污染物的排放,该文以居民小区产生的经大类粗分后的厨余垃圾为研究对象,以菌糠为膨松剂,设置15%、25%、35% 3个添加质量比（湿基）的堆肥处理,以纯厨余垃圾单独堆肥为对照处理,研究菌糠作为膨松剂对厨余垃圾堆肥过程中CH4、N2O、NH3和渗滤液排放的影响及其最佳添加比例。结果表明,堆肥过程中,添加菌糠可以完全避免厨余垃圾堆肥过程中渗滤液的产生;堆肥结束时,添加15%和25%菌糠的处理堆肥达到腐熟标准,但添加35%的菌糠使堆肥高温期缩短,不利于有机质分解;与对照处理相比,添加15%、25%和35%比例的菌糠均可以减少堆肥过程中CH4和NH3的累计排放量,且减排量与添加比例正相关,但只有添加15%菌糠的堆肥处理明显降低了N2O的排放量;添加质量比为15%和25%菌糠的堆肥处理,CH4和N2O排放总量比厨余垃圾单独堆肥分别减少45.8%、19.6%,而添加质量比为35%的菌糠使CH4和N2O排放总量为厨余垃圾单独堆肥的1.14倍（每t物料,干基）。综上,菌糠作为食用菌种植废弃物,可用作厨余垃圾堆肥膨松剂,在适宜的添加比例条件下,能够在避免堆肥过程中渗滤液产生的同时,减少CH4、N2O和NH3的排放量。研究结果可为厨余垃圾堆肥过程温室气体减排、氮素损失控制和工艺改进提供理论依据和试验基础。     

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.