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)。     

水稻油菜轮作稻田甲烷排放及其总量估算

利用静态箱/气相色谱法对川中丘陵区水稻油菜轮作稻田进行水稻全生长季CH4排放观测。结果表明,稻田CH4排放有明显的季节变化,呈“前低后高”的变化趋势,CH4排放峰出现在水稻抽穗扬花期;测定期内稻田CH4平均排放通量为6.20mg/m2.h。对影响稻田CH4排放的因素分析发现,淹水条件下水稻移栽到抽穗初期,水稻植株生长是影响稻田CH4排放的关键因素;水稻抽穗期到成熟期,温度是影响稻田CH4排放的关键因素。水稻油菜轮作稻田在水稻生长季中CH排放总量为173.96kg/hm2。     

三江平原寒地稻田CH_4、N_2O排放特征及排放量估算

利用静态暗箱-气相色谱法,于2003-2006年对三江平原寒地稻田CH4、N2O通量进行了为期4年的田间原位观测研究.结果表明:三江平原寒地稻田CH4和N2O排放具有明显的季节变化,水稻生长季淹水期是CH4排放的强源,稻田排水后CH4排放显著下降,休闲期CH4排放微弱或呈弱吸收汇,整个生长季CH4排放呈现单峰型态,并随水稻植株生长和叶面积指数而变化;水稻生长季和休闲期N2O排放通量都很小,冬季休闲期有时还出现微弱的吸收现象.生长季一般在施肥和表土落干时都会出现不同强度的排放峰,除了几次比较显著的排放峰值外,其它淹水状态下N2O排放很弱;温度和土壤水分状况是影响稻田CH4和N2O排放的重要因子,稻田积水深度和气体排放无明显的相关性;水稻植株对稻田土壤CH4排放起促进作用而对稻田土壤N2O排放起抑制作用;稻田氮肥用量增加可以降低土壤CH4排放,但却增加了N2O的排放.根据试验数据对三江平原地区寒地稻田CH4和N2O排放总量估算值分别为0.1035 Tg/a和0.0021 Tg/a.     

生物质炭还田对稻田甲烷的减排效果

为探讨不同生物质炭类型、输入量、还田时间和还田深度等因素作用下的CH4排放特征,采用静态箱-气相色谱法,通过向稻田土壤中施用3种类型的生物质炭（稻秆炭、麦秆炭、竹炭）,开展了水稻一个生长周期的室内观测试验。结果表明,3种类型的生物质炭输入后,对比空白处理,水稻产量显著性增加（P<0.05）,其中竹炭处理每盆实粒质量高达18.12 g,说明施用生物质炭可增加水稻产量;竹炭施用后稻田土壤CH4排放通量（80 mg/m2 h）显著低于稻杆炭和麦杆炭处理（P<0.05）,而稻杆炭和麦杆炭处理无显著性差异（P>0.05）,但都显著高于空白处理（P<0.05）,说明施用生物质炭可有效减少CH4排放。CH4排放通量与生物质炭用量负相关,CH4的排放通量随着生物质炭用量的逐渐增加而降低。同时,水稻移植前施用竹炭CH4排放通量（56.6 mg/m2 h）低于空白（96 mg/m2 h）及水稻成活前后（73.4和76.6 mg/m2 h）,但无显著性差异（P>0.05）,这与土壤氧化还原电位（Eh）变化相一致,说明生物质炭施用时间对稻田土壤CH4排放通量影响不大。此外,不同竹炭还田深度下的土壤CH4排放通量顺序为：中部输入（15 cm处输入）<表层输入（5 cm处输入）<深部输入（25 cm处输入）<空白（不输入生物质炭）,说明生物质炭中部输入更适用微生物生长和CH4气体减排。该研究可为太湖地区苕溪流域稻田增汇和温室气体减排提供参考。     

不同种类有机肥施用对一季稻田CH_4排放的影响

选取不同施肥处理的一季中稻田为研究对象,采用静态箱-气相色谱法对一季稻CH4排放通量进行手动观测。结果表明,与不施肥相比,各施肥处理CH4平均排放通量均有不同程度增加。其中稻草还田＋化肥处理（稻草处理）CH4平均排放通量为31.04mg·m-2·h-1,比化肥处理和猪粪＋化肥处理（猪粪处理）分别增加326.4%（P〈0.05）和211.7%（P〈0.05）,鸡粪＋化肥处理（鸡粪处理）比化肥和猪粪处理分别增加140.4%（P〈0.05）和75.7%（P〈0.05）。说明稻草还田和鸡粪处理显著增加稻田CH4排放通量,而猪粪处理与化肥无显著差异。同时对有关的环境因子进行分析表明,不同处理的土壤表层5cm温度、Eh与CH4排放通量存在显著相关关系;土壤pH值和水层厚度与稻田CH4季节排放通量相关性不明显。猪粪处理单位产量全球增温潜势（GWP）为0.83kg·kg-1,是较好的推荐施肥处理,对环境与产量之间效益的协调具有较好的作用。     

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。     

冬季淹水稻田CH4排放通量及其δ13C的时间变化特征

通过田间试验研究了持续淹水稻田冬季休闲期和水稻生长期CH4排放通量及其稳定性碳同位组成的时间变化。结果表明:CH4排放在冬季休闲期从4月份呈逐渐上升趋势,至6月份出现排放峰,为CH46.4 mg m-2h-1;水稻移栽后则迅速增加,于7月和8月出现两个排放峰,分别为CH423.1 mg m-2h-1和CH429.8 mg m-2h-1,此后急剧下降,末期稻田排水落干期间出现一个排放峰。冬季休闲期CH4排放总量为CH43.3 g m-2,占全年排放总量的8.9%。稻田排放的δ13CH4在冬季休闲期后期逐渐从-51‰上升至-44‰,然后下降至-56‰。水稻移栽后,δ13C值从-62‰迅速降至-68‰,然后慢慢上升至-60‰,并在较长一段时间内保持不变,后期再次富集13C。末期排水落干对排放δ13CH4影响显著。排放δ13CH4在水稻生长期较冬季休闲期低得多,原因在于冬季休闲期的CH4氧化率很高(60%～90%),而水稻生长期的CH4氧化率相对较低(10%～80%)。全观测期内,CH4排放通量的季节变化均与土壤温度显著正相关(p<0.01),与土壤Eh显著负相关(p<0.01),与δ13CH4呈显著负相关(p<0.05)。     

控制灌溉稻田的甲烷减排效果

为探讨节水灌溉水分调控对稻田甲烷（CH4）排放的影响,寻找节水减排的稻田灌溉模式,依据5a田间原位观测资料,分析控制灌溉稻田CH4排放规律及其减排效果。结果表明,控制灌溉稻田稻季CH4排放量为1.07±0.17 g/m2,较淹水灌溉稻田（6.49±0.17 g/m2）降低83.5%,差别极显著。本研究得到的中国东南部稻田稻季和全年CH4排放量均低于已有报道中的中国稻田CH4排放量,其中控制灌溉稻田全年CH4排放量低于世界大部分地区稻田。根据本研究结果估算中国稻田CH4排放总量为2.06 Tg/a,大面积推广控制灌溉后,中国稻田CH4排放量还将进一步下降。控制灌溉模式显著影响水稻全生育期稻田CH4排放通量的变化,削峰效果显著。控制灌溉稻田CH4排放通量在返青期至分蘖中期（移栽后18 d内）逐渐上升至最大值,然后逐渐减小,从水稻分蘖后期（移栽后21 d）开始至生育期结束均维持在较低水平。控制灌溉稻田CH4排放通量峰值为3.69 mg/m2·h,较淹水灌溉稻田降低69.0%。在持续降雨的作用下,控制灌溉和淹水灌溉模式下稻田CH4排放通量均呈现下降趋势。控制灌溉模式的土壤水分调控,使稻田经历一系列的脱水过程,改变了根层土壤的水气状况,减小了稻田CH4排放。控制灌溉模式在水稻全生育期的应用可显著地减少稻田CH4排放。     

冬季秸秆还田和土地管理对水稻生长期CH4排放的影响

利用田间试验研究了冬季3种土地管理方式下（种麦、休闲和淹水）秸秆施用（4800kg·hm^-2和0）对后续稻季CH。排放的影响。结果表明,休闲混施和休闲不施处理CH4平均排放通量显著高于种麦混施和种麦不施处理（P〈0．05）,但显著低于淹水混施和淹水不施处理（P〈0．05）;淹水混施处理CH4平均排放通量显著高于淹水不施处理（P〈0．05）,而休闲混施和休闲不施处理、种麦混施和种麦不施处理间无显著差异（P〉0．05）。水稻生长期CH4排放通量与5、10cm处土温呈极显著正相关（P〈0．01）,而与土壤肌无显著相关性（p〉0．05）。改冬季淹水和休闲稻田为种植小麦或在水稻移栽前对休闲稻田实施除草措施能显著减少稻田CH4排放量,是一种既增加农作物产量又能达到减少温室气体CH4排放的农业措施,具有很大的应用推广价值。     

下辽河平原潮棕壤撂荒地和人工林N2O、CH4排放研究

采用静态箱(暗箱)气相色谱法对下辽河平原潮棕壤撂荒地和人工林N2O、CH4排放进行了为期1年的原位测量,同时测量了土壤温湿度、气温,土壤NO3-N、NH4 -N含量等相关因子.结果表明,在观测期间内人工林地土壤的N2O排放通量明显高于撂荒地.撂荒地是大气CH4的源,而人工林则是CH4的汇.对人工林的观测结果表明,N2哦O排放与CH4排放之间存在负相关关系(R2=-0.351,p＜0.05,n=36);而撂荒地两种气体排放之间无明显相关关系.N2O排放通量和温度变化有很好的相关性.当土壤含水量在200 g/kg以上时,土壤含水量与CH4气体排放具有较好的正相关关系.     

Diurnal patterns of methane emissions from paddy rice fields in the Philippines

Methane (CH₄) emissions from rice paddies often show significant diurnal variations, most likely driven by diurnal changes of radiation and temperature in air, floodwater, and soil. Field measurements, however, are often scheduled at a fixed time of a given measuring day, thereby neglecting sub‐daily variations of CH₄ emissions. Here we evaluated diurnal patterns of CH₄ emissions from traditional paddy rice production as observed during field measurements in the Philippines. Field emissions were measured during three consecutive cropping seasons using an automated chamber and gas sampling system with fluxes being obtained every 4 h. Methane fluxes were monitored with a total of nine chambers during the dry seasons in 2012 and 2013 and 27 chambers during the wet season in 2012. Significant and consistent diurnal patterns of CH₄ emissions were mainly observed from the start of field flooding until the middle of cropping periods, i.e., periods with low leaf area of the rice crop. Our data show that disregarding the diurnal variability of fluxes results in an average overestimation of seasonal CH₄ emissions of 22% (16–31%) if measurements were conducted only around noon. Scheduling manual sampling either at early morning (7:00–9:00) or evening (17:00–19:00) results in estimations of seasonal emissions within 94–101% of the “true” value as calculated from multiple daily flux measurements. Alternatively, uncertainties of seasonal emissions can be reduced to an average of ≤3% by applying sinus function or Gauss function‐based correction factors. Application of correction factors allows the performance of flux measurements at any time of day. We also investigated N₂O emissions from rice paddies with respect to diurnal variations, but did not find, as in the case of CH₄, any significant and persistent diurnal pattern.     

小麦植株在麦田CH4交换中的作用及光照的影响

采用密闭箱/气相色谱法对中国科学院山东禹城实验站的麦田CH4通量进行观测,研究了土壤CH4通量、光照和遮光情况下的土壤-植物系统CH4通量,及植物、光照等因素对CH4通量的影响.试验采用小暗箱测定土壤CH4通量,采用暗箱和明箱测定土壤-植物系统CH4通量,同步观测了生物量、5 cm土壤温度、土壤水分及土壤NH4+含量.结果表明,麦田土壤和土壤-植物系统CH4通量均无明显的日变化,但季节变化显著;小麦的存在使土壤-植物系统CH4通量的季节波动加剧;小麦植株和光照促进麦田土壤-植物系统对CH4的吸收.此外,本研究发现在野外观测中,采用明箱覆盖土壤以及植物进行观测更能真实反映有植被覆盖的地表CH4通量状况.     

Rice yield reduction by chamber enclosure: a possible effect on enhancing methane production

Major rice growth characteristics and grain yield were compared between inside and outside of a chamber coverage area after a seasonal CH₄ and N₂O flux measurement using a closed chamber technique. Results show that only grain yield was significantly (P<0.01) reduced by chamber enclosure. There was no significant difference (P>0.05) in plant height, total straw weight, spike length, and average grain weight. Temperature increase during the gas flux measurement was likely the major cause for the observed grain yield decrease by sterilizing rice reproductive organs. Methane flux rates from rice fields were likely overestimated by using closed chamber technique because decreasing grain yield by chamber enclosure may result in more plant photosynthesis products released into soils to enhance CH₄ production. Analyzing CH₄ and CO₂ emission ratio from the rice field, after cutting the above-water part of rice plants, indicated that CH₄–C emission accounted for approximately 13% of the total CO₂ and CH₄–C emission during the major rice growing season.     

Effect of the long-term application of organic matter on soil carbon accumulation and GHG emissions from a rice paddy field in a cool-temperate region,Japan. -I. Comparison of rice straw and rice straw compost -

ABSTRACT

The influence of the long-term combination of rice straw removal and rice straw compost application on methane (CH₄) and nitrous oxide (N₂O) emissions and soil carbon accumulation in rice paddy fields was clarified. In each of the initial and continuous application fields (3 and 39?51 years, respectively), three plots with different applications of organic matter were established, namely, rice straw application (RS), rice straw compost application (SC) and no application (NA) plots, and soil carbon storage (0?15 cm), rice grain yield and CH₄ and N₂O fluxes were measured for three years. The soil carbon sequestration rate by the organic matter application was higher in the SC plot than in the RS plot for both the initial and continuous application fields, and it was lower in the continuous application field than in the initial application field. The rice grain yield in the SC plot was significantly higher than those in the other plots in both the initial and continuous application fields. Cumulative CH₄ emissions followed the order of the NA plot < the SC plot < the RS plot for both the initial and continuous application fields. The effect of the organic matter application on the N₂O emissions was not clear. In both the initial and continuous application fields, the increase in CH₄ emission by the rice straw application exceeded the soil carbon sequestration rate, and the change in the net greenhouse gas (GHG) balance calculated by the difference between them was a positive, indicating a net increase in the GHG emissions. However, the change in the GHG balance by the rice straw compost application showed negative (mitigating GHG emissions) for the initial application field, whereas it showed positive for the continuous application field. Although the mitigation effect on the GHG emissions by the combination of the rice straw removal and rice straw compost application was reduced by 21% after 39 years long-term application, it is suggested that the combination treatment is a sustainable management that can mitigate GHG emissions and improve crop productivity.     

Mechanisms of biochar decreasing methane emission from Chinese paddy soils

Paddy fields are one of the largest anthropogenic sources of global CH₄ emission. A decrease in paddy CH₄ emission can contribute significantly towards the control of global warming. Recent studies have demonstrated that the application of biochar in paddy soils has such a capability, but its underlying mechanism has yet to be elucidated. In this investigation, we studied CH₄ emission, methanogenic archaeal, as well as methanotrophic proteobacterial communities, from microcosms derived from two paddy soils, Inceptisol and Ultisol. Both soils were amended with biochar at different pyrolysis temperatures (300 °C, 400 °C and 500 °C) at field condition. The soil CH₄ flux was monitored across whole rice season in 2010; the functional guilds communities were analyzed by PCR–DGGE and real-time quantitative PCR (qPCR). It is found that paddy CH₄ emissions significantly decreased under biochar amendments, which, interestingly, didn't result from the inhibition of methanogenic archaeal growth. qPCR further revealed that biochar amendments (1) increased methanotrophic proteobacterial abundances significantly, and (2) decreased the ratios of methanogenic to methanotrophic abundances greatly. These results shed insight on the underlying mechanism of how biochar decreases paddy CH₄ emission. This knowledge can be applied to develop a more effective greenhouse gas mitigation process for paddy fields.     

Controlled irrigation and drainage of a rice paddy field reduced global warming potential of its gas emissions

The effect of controlled drainage on methane (CH₄) and nitrous oxide (N₂O) emissions from a paddy field under controlled irrigation (CI) was investigated by controlling the sub-surface drainage percolation rate with a lysimeter. CI technology is one of the major water-saving irrigation methods for rice growing in China. Water percolation rates were adjusted to three values (2, 5, and 8 mm d^?1) in the study. On the one hand, the CH₄ emission flux and total CH₄ emission from paddy fields under CI decreased with the increase of percolation rates. Total CH₄ emissions during the growth stage of rice were 1.83, 1.16, and 1.05 g m^?2 in the 2, 5, and 8 mm d^?1 plots, respectively. On the other hand, the N₂O emission flux and total N₂O emissions from paddy fields under CI increased with the increase of percolation rates. Total N₂O emissions during the growth stage of rice were 0.304, 0.367, and 0.480 g m^?2 in the 2, 5, and 8 mm d^?1 plots, respectively. The seasonal carbon dioxide (CO₂) equivalent of CH₄ and N₂O emissions from paddy fields under CI was lowest in the 2 mm d^?1 plot (1364 kg CO₂ ha^?1). This value was 1.4% and 19.4% lower compared with that in the 5 and 8 mm d^?1 plots, respectively. The joint application of CI and controlled drainage may be an effective mitigation strategy for reducing the carbon dioxide equivalents of CH₄ and N₂O emissions from paddy fields.     

Is burial of wheat straw in ditches a way to reduce CH4 emissions from rice cultivation?

Abstract

Burial of wheat straw in ditches and incorporation of wheat straw are the two main ways of returning wheat straw prior to rice cultivation in China. To examine the effect of burying wheat straw in ditches on CH₄ emissions from rice cultivation, a field experiment was conducted at Yixing, Jiangsu, China in 2004. CH₄ flux was measured using a closed-chamber technique in three treatments (CK, no wheat straw application; WI, evenly incorporating 3.75 t ha^?1 wheat straw into the 0.1 m topsoil; WD, burying 3.75 t ha^?1 wheat straw in 0.14-m deep by 0.25-m wide ditches). Seasonal CH₄ emissions ranged from 49.7 to 218.4 kg CH₄ ha^?1. The application of wheat straw in these two ways significantly increased CH₄ emissions by 4.0-fold and 4.4-fold, respectively (P < 0.05). Although CH₄ flux from the non-ditch area in the WD treatment was as low as that in the CK treatment, it was counter-balanced by extremely high CH₄ flux from the ditch, which was approximately 6.0-fold as much as that from WI, leading to comparability between treatments WI and WD in total CH₄ emissions (P > 0.05). No significant difference was observed between the three treatments in grain yield (P > 0.05). The results indicated that burial of wheat straw in ditches is not a way to reduce CH₄ emission from rice cultivation.     

土壤质地、温度和Eh对稻田甲烷排放的影响

本文报道在田间条件下,土南地,温度和Ｅｈ影响稻田ＣＨ４排放通量的研究结果。中国科学院封丘生态试验站的小区试验表明,在当地常规水分管理即间歇灌溉条件下,供试小区和妥田的ＣＨ４平均排放通量仅为０．１６－１．８６ｍ ｇＣＨ４／ｍ＾２ｈ。     

High-Time Resolution Analysis of Diel Variation in Methane Emission from Flooded Rice Fields

Methane (CH₄) emission from flooded rice fields was measured hourly over 24 h for rice (Oryza sativa L.) seasons in 2008 and 2009. The objectives of this study were to identify typical diel variation in CH₄ emission and to estimate the best time of day for optimum extrapolation of daily CH₄ emission. Our results showed distinct diel variation in CH₄ emission, which exhibited a maximum at 14:00–15:00 and a minimum at midnight. About 5.2–5.6% of total CH₄ emitted per day (110–160 mg CH₄ m^?2 d^?1) was released at 14:00–15:00. The diel pattern of CH₄ emission resembled that of air temperature (T_a). The T_a coupled with solar radiation could cause a difference in partial pressure of CH₄ (DPPC) through the gas conduit of the plant. The best extrapolation of daily CH₄ emission was achieved with data observed at 10:00–11:00. We concluded that DPPC-induced CH₄ emission is an important mechanism causing diel variation.     

不同施肥处理稻田甲烷和氧化亚氮排放特征

采用静态箱－气相色谱法对长期不同施肥处理(NPKS、CK、NPK和NKM)的稻田CH₄和N₂O排放进行了观测。结果表明，稻田CH₄和N₂O排放季节变化规律明显不同，二者排放通量季节变化呈显著负相关(p<0.01)。与单施化肥和CK相比，施用有机肥显著促进CH₄排放，排放量最高的NPKS处理早晚稻田排放量分别是：526.68 kg/hm²和1072.92 kg/hm²。对于N₂O排放，早稻田各处理间差异不显著，NPK处理排放量最大，为1.48 kg/hm²；晚稻田各处理差异极显著(p<0.01)，NPKS处理排放量最大，为1.40 kg/hm²。晚稻田CH₄排放通量和10 cm土层温度及土壤pH值相关极显著(p<0.01)，并与二者存在显著的指数关系。没发现N₂O排放通量与温度及pH值间存在显著相关。稻田CH₄和N₂O排放受多种因素影响，但对全球变暖的贡献率CH₄远大于N₂O。NPKS处理的增温潜势最大，NPK处理的最小。