气候变化研究进展, 2023, 19(5): 541-558 doi: 10.12006/j.issn.1673-1719.2023.136

甲烷排放的特点、控制及成本效益专栏

稻田甲烷排放现状、减排技术和低碳生产战略路径

秦晓波,, 王金明, 王斌, 万运帆

中国农业科学院农业环境与可持续发展研究所/中国农业科学院农业农村碳达峰碳中和研究中心/农业农村部农业环境重点实验室,北京 10008

Status of methane emissions from paddy fields, mitigation technologies and strategic pathways for low-carbon production

QIN Xiao-Bo,, WANG Jin-Ming, WANG Bin, WAN Yun-Fan

Institute of Environment and Sustainable Development in Agriculture / Agricultural and Rural Carbon Peak and Carbon Neutral Research Center, Chinese Academy of Agricultural Sciences/Key Laboratory for Agro-Environment, Ministry of Agriculture and Rural Affairs, Beijing 100081, China

收稿日期: 2023-06-21   修回日期: 2023-07-13  

基金资助: 国家重点研发计划(2021YFD1700202-05)
江西省中央引导地方科技发展资金项目(20221ZDH04057)
国家自然科学基金(41775157)

Received: 2023-06-21   Revised: 2023-07-13  

作者简介 About authors

秦晓波,男,研究员,qinxiaobo@caas.cn

摘要

作为第一大主粮作物,水稻在我国粮食和重要农产品稳定安全供给体系中占有举足轻重的地位,其低碳生产不仅关乎国家双碳战略的推进,更对国家粮食自给率提升、国民膳食营养改善和气候外交的实施意义重大。文中从我国稻田甲烷(CH4)排放现状、减排技术和低碳生产战略等方面,系统论述了低碳可持续稻谷生产系统的实现路径。近年来,我国水稻种植面积尽管有所波动,但水稻单产持续增加,2021年平均亩产高达474.2 kg,创历史新高。与此同时,稻田也是我国CH4主要排放源(1.87 亿t CO2e),占我国农业活动CH4排放总量的40.1%。因此,面对水稻可持续生产、未来气候变化不利影响及气候外交的多重挑战,稻田CH4减排要充分考虑水分、肥料、品种、耕作和菌剂产品等的综合运筹,以人为强化措施为主,辅以基于自然的解决方案,建立主产稻区适用“抑菌减排-增腐固碳-良种丰产-减投增效”的“抑增良减”技术体系。实施覆盖作物种植、免耕轮作、高产低排品种选育、覆膜保墒、菌剂增效产品、智能机具、合理密植、肥蘖脱钩、干湿交替和增氧耕作等十大技术模式,在确保稻米有效供给的同时减排增碳,实现水稻可持续绿色高质量发展。

关键词: 水稻; 粮食安全; 甲烷(CH4; 减排技术; 低碳生产战略

Abstract

As the largest staple food crop, rice plays a pivotal role in China’s stable and safe supply system of grain and important agricultural products. It can be seen that low-carbon rice production is not only related to the promotion of the national dual-carbon strategy, but also of great significance for the improvement of the national grain self-sufficiency rate, the improvement of national dietary nutrition and the implementation of climate diplomacy. This paper systematically discusses the realization path of low-carbon sustainable rice production system from the aspects of China’s rice field methane emission status, emission reduction technology and low-carbon production strategy. In recent years, although the rice planting area in China has fluctuated, the yield per unit area of rice has continued to increase. In 2021, the average yield per mu (1 mu≈667 m2) reached 474.2 kg, a record high in history. At the same time, rice fields are also the main source of methane (CH4) emissions in China (187 Mt CO2e), accounting for 40.1% of the total methane emissions from agricultural activities in China. Therefore, facing the multiple challenges of sustainable rice production, adverse impacts of climate change in the future, and climate diplomacy, CH4 emission reduction in paddy fields must fully consider the comprehensive planning of water, fertilizers, varieties, tillage, and inoculum products. It is necessary to establish a technical system based on human-enhanced measures supplemented by Nature-based Solutions, for inhibiting growth, improving production and increasing efficiency based on near-natural regulation and artificial enhancement, which is applicable to the main rice-producing areas. On this regarding, the implementation of cover crop planting, no-tillage rotation, high-yield and low-emission variety breeding, mulching and moisture conservation, bacterial agent synergistic products, intelligent machinery, reasonable dense planting, decoupling of tillers, alternating wet and dry, and aerobic farming, etc., to ensure the effective supply of rice, reduce emissions and increase carbon, and achieve sustainable, green and high-quality development of rice.

Keywords: Rice; Food security; Methane (CH4); Emission reduction technology; Low-carbon production strategy

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本文引用格式

秦晓波, 王金明, 王斌, 万运帆. 稻田甲烷排放现状、减排技术和低碳生产战略路径[J]. 气候变化研究进展, 2023, 19(5): 541-558 doi:10.12006/j.issn.1673-1719.2023.136

QIN Xiao-Bo, WANG Jin-Ming, WANG Bin, WAN Yun-Fan. Status of methane emissions from paddy fields, mitigation technologies and strategic pathways for low-carbon production[J]. Advances in Climate Change Research, 2023, 19(5): 541-558 doi:10.12006/j.issn.1673-1719.2023.136

甲烷是典型的短寿命气候污染物,不仅具有明显的温室效应,还有助于形成地面臭氧,形成空气污染和破坏臭氧层。IPCC第六次气候变化评估报告(AR6)指出“持续减排甲烷,可减少全球地表臭氧形成,有助于改善空气质量,并长期降低地表温度”。减少人为甲烷排放是快速降低变暖速度的最具成本效益的战略之一。

近年来,国际社会对全球甲烷减排的关注度日益增强。第26次公约缔约方大会上,美国和欧盟等100多个国家/地区形成了“全球甲烷承诺”联盟,提出了到2030年将全球人为甲烷排放量在2020年水平上减少30%的雄心目标;甲烷减排的目标在COP27得到重申。

目前国内外围绕甲烷排放的现状与趋势、甲烷减排与控制的政策措施、甲烷排放源的检测与方法学研究以及甲烷减排技术、经济成本效益研究等方面展开广泛深入的研究,其成果可为制定甲烷减排政策措施,参与应对气候变化国际谈判,维护国家利益,实现2060年碳中和目标提供科学支撑。

本专栏得到国内科学家的广泛关注与支持。阐述了我国稻田甲烷排放及低碳生产的战略路径,分析了科学健康的膳食对农业甲烷排放的影响;针对区域废弃物处理的甲烷排放与管理进行了分析,并对比研究了G7国家废弃物领域甲烷排放的驱动力,对我国开展相关的工作具有重要的借鉴意义。

引言

到21世纪末将全球温升限制在1.5℃(相比工业化前)是全人类面临的重大挑战,但根据2021年各国宣布的国家自主贡献还很难实现这个目标。2019年,全球甲烷(CH4)浓度已经达到1866×10-9,相比1750年增加了156%[1],是三种主要温室气体中增加速度最快的。全球范围内,水稻生产是CH4重要的人为排放源,2019年全球稻田CH4排放高达10亿t CO2当量(CO2e),占农业生产总碳排放的15.81%[1]。政府间气候变化专门委员会(IPCC)第六次评估报告综合报告[1]指出,1850年以来观测到的全球变暖是人为——主要是二氧化碳(CO2)和CH4造成的变暖。在将温升控制在1.5℃的情景中,到2030年和2040年,全球CH4排放量要分别比2019年减少34% [21%~57%]和44% [31%~63%],这个目标为全球CH4减排行动带来了巨大压力。

水稻生产是我国农业CH4重要来源,从历年国家温室气体清单数据来看,我国水稻种植CH4排放在2005年达到最高,之后维持在较低水平。2014年,我国水稻种植CH4排放1.87亿t CO2e,占农业温室气体总排放的22.58%[2]。近年来,我国在稻田CH4减排机理、技术及路径方面开展了大量研究[3-4]。然而,农业温室气体减排仍受成本、农业系统多样性和复杂性以及产量提升需求增加等因素的限制[5],导致稻田高质量发展和低碳转型路径仍不清晰。鉴于水稻在全球食物系统的重要性,探索水稻低碳生产战略路径,不仅将对缓解气候变化有重要贡献,以稻田CH4减排增产为代表的农业减排行动也将直接影响2030年联合国可持续发展目标的实现。当前,虽然我国农业碳排放总量较高,但单位农业GDP碳排放强度(1.42 t CO2e/万元)、人均碳排放量(8.93 t CO2e/人)及人均农业人口碳排放量(0.96 t CO2e/人)均远低于美国等发达国家[6]。可见,在我国农业高速发展的同时,已经实现了较低的碳排放,但另一个问题随之而来,在国家粮食安全和气候外交压力的双重驱动下,水稻生产低碳转型的关键技术和战略路径如何?

我国是世界人口第二位的传统农业大国,水稻生产的低碳转型受国家粮食安全、全球气候变暖和资源环境的多重约束。一方面,水稻是我国主要的粮食作物,在国家粮食安全体系中占有突出地位。2021年,我国水稻种植面积达4.49亿亩(1亩≈667 m2),分别占农作物、粮食作物和谷物总播种面积的17.74%、25.44%和29.87%[7-8]。近年来,受区域极端气候事件和种植结构调整等因素影响,我国水稻种植面积有所波动,2021年比2020年播种面积减少232.1万亩,减幅0.5%;其中早稻和中晚稻播种面积分别为0.71亿亩和3.78亿亩,分别比2020年减少0.3%和0.5%[8]。尽管如此,我国水稻单产持续增加,2021年平均亩产达到474.2 kg,创历史新高,其中早稻和中晚稻分别达到394.5 kg和489.21 kg[8]。近年来,我国政府加快了相关技术的推广应用,如耕地轮作休耕试点、粮食绿色高质高效行动、持续推进化肥减量增效和农药减量控害、加强耕地质量保护与提升及加强基层农技推广体系改革等,确保了在新形势下我国水稻产业绿色高质量快速发展。另一方面,作为对气候变化影响较脆弱的部门,我国农业特别是水稻生产已经并将继续受到全球变暖的影响。IPCC第六次评估报告综合报告认为,未来气候变化将通过自然和人类系统产生严重影响并导致地区差异相应增加[1],因此,在应对国家粮食安全和气候变化不利影响双重压力下,还需加强区域针对性减排增产技术的研发推广。

因此,本文综述了我国稻田CH4排放现状、减排技术和低碳生产战略路径相关研究进展,以期为我国水稻产业低碳绿色高质量发展提供科学支撑。在国家CH4整体减控战略和稻米稳定安全供给的前提下,我们重点关注的科学和产业问题包括:(1)为确保水稻可持续生产、减缓气候变化不利影响,如何揭示丰产减排固碳互作机制并实现多目标调控途径;(2)针对种植结构调整、低碳高效品种缺乏、农机农艺不同步、秸秆无害化与快腐固碳难兼顾等问题,如何构建基于近自然调控和人为强化的水稻低碳生产技术体系,从而实现水稻生产低碳转型。

1 稻田甲烷排放现状

近30年(1992—2014年)来,我国稻田CH4排放呈先下降后上升然后保持稳定的变化趋势,2014年我国稻田CH4排放量为1.87亿t CO2e(图1表1),占我国农业活动CH4排放总量的40.06%(从历年数据来看,贡献占比有上升的趋势),贡献了全球稻田CH4排放的18.13%(表1)。从全球范围来看,水稻种植贡献农业活动CH4排放的17.72%(14.08%~24.32%)[5],其中以EDGAR(美国电子数据收集、分析和检索系统)的占比估算(2010—2019年)最高,而全球碳项目(GCP)中全球甲烷评估(GMB)[9]的估算值(2017年,14.08%)最低,且与IPCC AR6的估值(2019年,15.82%)接近。造成各种评估结果差异的原因是多方面的,其中CH4全球增温潜势(GWP,100年尺度)的取值固然是一个因素,但清单编制或评估过程的不确定性也是不容忽视的原因。就我国国家温室气体清单编制而言,其农业活动排放清单不确定性范围为-19.2% ~ 20.4%[2]

图1

图1   我国水稻生产和稻田CH4排放现状

注:数据来源于《中国统计年鉴(1979—2021年)》和《中华人民共和国气候变化第二次两年更新报告》。

Fig. 1   Current situation of rice production and methane emission from paddy field in China


表1   中国和全球稻田CH4排放现状

Table 1  Methane emission from China and global paddy field

注:1) Emissions Database for Global Atmospheric Research,https://edgar.jrc.ec.europa.eu/;2) https://www.fao.org/faostat/en/#data/GT;3) https://www.epa.gov/gmi;4) https://www.globalcarbonproject.org/

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我国水稻生产CH4排放占比较高,也间接反映了水稻种植在我国农业生产和粮食供给中的重要地位。我国是传统农业大国,过去几十年,依靠科技进步和技术革新,我们以9%的耕地养活了全球20%的人口,这一“中国奇迹”震惊了世界,也为全球粮食供应和饥饿人口的减少做出了卓越贡献。因此,我国农业排放包括水稻种植CH4排放,都属于典型的生存排放,而且我国碳排放主要来自能源活动和工业生产过程,农业碳排放贡献占比较低。农业将继续为我国稳产保供提供基础支撑,也将继续为保障国家粮食安全和减缓全球气候变化做出贡献。2023年3月发布的《中国农业农村低碳发展报告(2023)》[6]也强调了我国农业生存排放的特性及主要农作物温室气体排放降低的趋势,考虑到未来我国国民经济发展,随着绿色低碳转型发展战略及技术普及,我国农业温室气体排放强度将继续降低。

2 稻田甲烷减排技术

稻田CH4产生的生态系统过程源于一连串复杂的发酵过程,首先是有机大分子到乙酸、羟基酸、醇类、二氧化碳及氢气的初级发酵过程,其次是醇类和羟基酸到醋酸盐、氢气和二氧化碳的次级发酵过程,这一过程最终在产甲烷古菌的参与下转化为CH4。水稻田CH4的排放起始于水稻土壤CH4的产生、再氧化以及传输至大气的整个过程[10-11]。CH4生物成因主要产生途径有4条,即氧甲基型、甲基型、乙酸型和氢型;其中,乙酸和氢型是最常见的CH4生成途径,二者分别可占陆地生态系统CH4生成的67%和33%[12]。最新研究则证实了一种新型产甲烷古菌可以直接氧化长链烷基烃而不需要通过互营代谢来完成,从而提出第5条产CH4途径[13],即烷基型生物产CH4途径,这一新发现也启迪了我们新的CH4减排途径的可能性,CH4产生和排放机理与监测手段的科技创新也促进了减排技术的研发。

2.1 抑菌减排

产甲烷古菌和甲烷氧化菌在稻田CH4产生和排放过程中起决定性作用。国外研究证实许多化学物质如溴甲烷-磺酸、氯仿和氯甲烷等可抑制甲烷菌的活性,肥料型的甲烷抑制剂如碳化钙胶囊能使稻田CH4排放降低90.8%[14]。Cho等[15]在韩国的研究发现,利用醋酸纤维素搭配乙烯利抑制了43%的稻田CH4产生,其效果类似于其他众所周知的产甲烷抑制剂(2-溴乙磺酸盐、2-氯乙磺酸盐、2-巯基乙磺酸盐)[16-17],原因在于其显著降低了水稻土中古菌群落以及产甲烷菌的相对丰度和表达水平。然而,尽管这些非特异性抑制剂的市场价格较低,但它们对土壤具有广泛的非靶向作用,如果大量连续施用,可能会破坏土壤健康[15]。例如,Pramanik等[18]通过盆栽试验发现水稻种植过程中施用2.5 mg/kg的EDTA(乙二胺四乙酸)可将CH4排放量减少多达20%,但显然也会降低土壤微生物的活性。鉴于此,甲烷抑制剂还尚未被大范围应用,即使它们抑制CH4排放的潜力高于稻田常规农艺实践所能达到的水平。因此,新型环境友好的CH4抑制产品有待进一步研发。除抑制剂外,EM(有效生物菌剂)也有较好的增产减排效果:苗曼倩等[19]在江苏稻田的试验首次揭示了EM的CH4抑制效果(平均可达59%),其原因在于EM中含有的光合细菌作用;此外,不同时期EM施用效果有差异,在分蘖-拔节期这一CH4排放高峰期内追施EM固体肥料后,抑制作用最明显;从整个生育期看,EM处理水稻产量显著提高。王斌等[20]在荆州的研究则发现EM可使双季稻CH4排放减少34.9%,同时增产3.2%;王斌等[21]和蔡威威等[22]也发现了EM的氮素利用率提升和增产效应(3.9%~13.5%)。尽管有效生物菌剂具有一定的减排增产效果,但目前研究还较少,限制了其进一步推广应用。

抑制剂的研发与应用,针对的是CH4产生过程,而另一类产品可以增强CH4的氧化,故可称为增氧剂。Shaaban等[23]发现白云石搭配氮肥施用,可以增强55%WFPS(充水孔隙度)条件下的CH4吸收(氧化),从而可以减少酸性土壤中的CH4排放。Khatun等[24]则研究了磷石膏作为土壤有机改良剂的同时,增强CH4氧化过程的效果,发现相比生物炭等其他制剂,磷石膏处理有效地控制了CH4排放,从而提出在盐渍土中将磷石膏和生物炭与推荐的氮磷钾锌肥料联合施用,可能是通过增加K+/Na+、Ca2+/Na+比率来提高水稻对盐分耐受性同时减排CH4的良好做法。Zhou等[25]的研究则认为,受气候变暖胁迫的植物会释放乙烯,从而显著抑制CH4氧化,但ACC(1-氨基环丙烷-1-羧酸盐)脱氨酶通过减少乙烯生物合成来调节植物应激反应,同时可维持土壤中的CH4氧化率。目前,这种通过使用ACC脱氨酶研究气候变暖引起的植物胁迫增强乙烯渗出对CH4氧化的潜在影响还有待进一步加强。

2.2 促腐增碳

众所周知,秸秆还田是最有效的土壤有机质补充方式之一,也是我国大力推行的保护性耕作措施,但新鲜秸秆还田由于有机质含量较高将极大促进稻田CH4的排放,如何在秸秆还田的同时降低CH4的产生,是稻田固碳减排的一个重大挑战。为此,有学者研发了腐解剂、冬闲期还田、过腹还田和生物质炭资源化利用[26-27]等不同还田技术和产品,以期缓解新鲜秸秆还田后CH4大量排放的问题。其实,稻田CH4的产生除了产甲烷菌的生化介导作用,更重要的在于土壤有机质对产CH4碳源的贡献。由于内外源有机碳(秸秆、有机肥、微生物同化、根系及土壤本底碳)对CH4产生有重要影响,如何增加土壤碳库的稳定与固持、减少其溶出和矿化损失[28],从而在源头抑制CH4的产生是稻田减排固碳的关键。我国农业部门也越来越多地采用将秸秆与微生物接种剂(细菌和真菌的混合物,旨在加速秸秆分解)结合起来的方法,如Liu等[29]针对稻麦轮作系统,采用了在小麦季将水稻秸秆与接种剂(微生物菌剂和金葵子菌剂)结合的方法,有效降低了轮作系统整体温室效应。另外,对于我国广泛分布的稻麦轮作系统,将秸秆施用时间从水稻季节转移到非稻季(小麦季)可以有效避免高CH4排放,这种做法已被广泛应用[30-31]。Qin等[32]对连续40年长期施肥试验的数据分析后也认为,秸秆施用和粪肥改良时机对提高水稻产量和降低碳足迹至关重要。可见,针对稻田秸秆还田的增碳促排效应,因地制宜适时通过还田时间、还田方式及新式促腐快腐菌剂产品的调节,可以实现土壤增碳的同时降低CH4排放。

实际上,作为单项技术,通过不同形式的秸秆还田(稻草粉碎或腐熟还田),能促进土壤微生物碳利用和土壤团聚体稳定性[33],达到固碳减排的目的。从土壤养分和微生物化学计量学角度讲,通过氮肥和稻草配施调控总体碳氮比,促进外源碳向小分子官能团降解转化,以此促进团聚体物理保护作用,提升土壤碳库的固持,加强稻田土壤碳汇功能,但目前这种秸秆还田与氮肥优化等措施的结合程度还有待提升[34]。刘天奇等[35]研究发现,通过调控稻草和氮肥配比,提升土壤团聚体吸附外源颗粒有机碳功能,相比常规稻草管理模式提高土壤碳库闭蓄态颗粒有机碳储量32.3%。另外,稻草还田还可以结合增氧耕作等综合运筹,实现水稻产量提升和CH4减排的协同。张俊等[36]发现,以稻草切碎匀抛、田间旱耕湿整和增密调氮控水为关键技术,改善耕层土壤通透性和水稻通气组织的输氧能力及抗倒防衰性能,提高耕层和水稻根际氧含量,可实现稻草还田下水稻丰产与CH4减排协同。该技术体系在我国水稻主产区大面积示范中,高产条件下取得氮肥利用增效30.2%~36.0%、稻作节本增收8.3%~9.7%和CH4减排31.7%~75.7%的显著效果。上述稻草还田与氮肥、耕作相关措施的优化调控,实现了CH4减排和水稻增效的共同目的,氮素利用率和栽培措施的优化提升,间接促进了稻草腐解和碳素的固持,因此达成土壤增碳和CH4减排的双赢目标。

2.3 良种丰产

良种是水稻丰产的保证,而因其基因型、生长特性、通气组织传输能力的差异,导致筛选培育高产低CH4排放品种成为可能(图2)。诸多研究发现,不同水稻品种的CH4排放率差异较大[27,38-40]。如Bhattacharyya等[41]对不同水稻品种CH4排放速率、根系分泌物、根氧化酶活性和茎秆通气组织孔隙空间进行了研究,发现不同品种的CH4平均排放量在0.86~4.96 mg/(m2∙h)之间,并且CH4排放率在短期品种中最低,其次是中长期品种。在中短期品种中,平均每单位稻谷产量CH4排放率的温室气体排放强度也最低(0.35 kg CO2e/kg)。多数研究认为,水稻品种对CH4排放的影响主要与水稻生长性能有关,即分蘖数、植物地上和地下生物量[42-44]。尽管许多研究发现水稻生物量与CH4通量之间存在显著的正相关关系[45-46],但也有不少相反结果的报道[27,37,47],这强调了在生物量这一重要因素之外,水稻植物氮肥利用效率的差异[48-50]以及不同品种对根系CH4产生和氧化菌群落的影响。总之,这种水稻品种之间的排放差异表明从育种基因型角度培育低排放水稻品种的可行性,但目前对基因型如何影响参与CH4循环的微生物群的了解有限[51]。如Balakrishnan等[37]通过现场筛选CH4排放、高温、臭氧耐受性和氮利用效率来识别基因型变异,对于启动成功的育种计划以开发能够提高气候适应能力的水稻品种是必要的[52]。Liechty等[51]则在整个生长季节对高CH4排放品种(Sabine)和低CH4排放品种(CLXL745)的根际、根平面和内圈微生物组进行了分析,以确定与CH4相关的古细菌群落的变化,揭示了一个复杂的微生物相互作用网络,发现植物基因型依赖因素可在该网络上影响CH4产生和排放。2015年,Su等[53]通过基因编辑手段发现了高籽粒碳分配的新型低CH4排放水稻品种SUSIBA2,认为优化光合产物分布对于提高水稻产量和减少CH4排放非常重要,这为从基因编辑角度培育低CH4品种开创了先河。Du等[54]后续对该品种低CH4性状及土壤碳和微生物群落进行了综合分析,发现基于该基因的水稻向土壤释放的碳减少,早晚稻(平均50%减排率)和粳籼稻品种(粳稻高于籼稻)均有较大的CH4减排差异,预测具有大麦HvSUSIBA2基因的分子水稻育种可提高谷物的光合产物通量,从而提高水稻产量并减少稻田中的CH4排放。目前,这种基于基因编辑的水稻品种改良实现CH4减排的探索还较少,未来也面临水稻产业发展和国家粮食安全保障等诸多挑战。

图2

图2   高产低排放水稻品种选育改良方向[37]

Fig. 2   High-yield and low-emission rice variety breeding and improvement direction[37]


除低排放高产水稻品种的基因编辑、分子育种和超短生育期品种培育的探索外[53],更多研究关注于低排放品种与水稻植株通气组织、根系分泌及植株生理生态特性的关系等方面。Soremi等[55]收集了有关CH4排放、表型、生理、根性状和谷物产量的数据,发现不同品种的籽粒产量、根长和根表面积差异显著。稻田土壤CH4向大气传输3个途径中最主要的是水稻体内通气组织,这一传输途径占稻田向大气CH4排放总量的80%~90%[40,56-57]。有研究发现,水稻植株体传输CH4的能力与其生长阶段密切相关[41]。Mosier等[58]认为,在生长季早期,水稻植株发育较小的情况下,绝大部分CH4通过气泡形式传输,大约1个月后,48%的CH4排放是由水稻植株脉管传输的,而到生长季后期,这种方式的传输占该时期CH4总排放量的90%~97%[59-60]。可见,CH4排放速率受通气组织取向、根系分泌和生物量产生速率的控制,这些是栽培品种的关键特定性状,已确定的性状与特定生态环境中种植品种的持续时间和适应性密切相关。因此,可根据生态、持续时间和具有较少的CH4排放潜力来选育水稻品种。Chen等[61]发现,根的形态和生理特征(即根干重、根长、根氧化活性和根径向氧损失)与CH4通量呈负相关,原因在于根系分泌物(苹果酸、琥珀酸和柠檬酸)促进了甲烷氧化菌的丰度和活性。Kim等[62]研究了水稻根横切面(RTS)、通气组织面积和通气组织百分比的遗传变异,发现RTS和通气组织面积与CH4排放量显著相关,因此认为根横切面面积可作为选择低CH4排放品种的一种手段。Balakrishnan等[51]则发现通过有效分蘖数和很少通气组织而培育的新植物型(NPT)水稻品种被认为对减少根系分泌物有效,已针对这些参数进行表型分析的基因型可用作育种计划中的供体[63]。Wang等[64]则指出,根系氧化潜力高、收获指数高、非生产性分蘖数少,是培育低CH4排放的理想水稻品种的育种目标,培育具有最少非生产性分蘖并降低根系渗透性的新品种可以减少CH4排放,这将是减少CH4排放的有希望和经济的方法。

另外,从水稻栽培角度来讲,实施综合作物管理(ICM,integrated crop management)[65]和水稻集约化系统(SRI,System of Rice Intensification)[66]可以提高水稻整体栽培质量和产量,同时降低CH4排放强度,确保良种发挥稳产减排固碳的效用。如通过ICM,整合多种技术,引入包括增加植物密度、优化氮素投入、交替润湿和适度土壤干燥(AWMD)以及施用有机肥等措施的联合实施,从水稻栽培整体效能提升上减少CH4排放。Setyanto等[65]发现ICM下,水稻根系形态生理性状与籽粒产量呈显著正相关,而根长、比根长、ROA、根总和活性吸收表面积与总CH4排放呈显著负相关,而根系分泌物中苹果酸、琥珀酸和乙酸的浓度比当地农民传统实践高。这些结果表明,ICM可以通过改善水稻根系形态和生理性状来实现提高粮食产量和减少温室气体排放的双重目标。

2.4 减投增效

我国于2015年提出化肥零增长计划并于2017年底实现了全国化肥总量零增长,但Li等[67]和Qin等[68]研究结果表明,我国主要粮食种植系统都还存在一定的氮盈余,可见,我国农业还需要进一步减量增效。同样,稻田CH4主要由过量灌溉激发的土壤厌氧菌产生,因此,节水节氮高效生产是稻田CH4减排的重要选择。从节水节氮角度看,减少稻田CH4排放的措施主要包括[5]改进水资源管理(单一排水和多次排水)、改进作物残茬管理[69-70]、改进施肥(使用缓释肥料和特定养分施用等),以及土壤改良剂(包括生物炭和有机改良剂等)[26,71]。这些措施不仅具有缓解潜力,而且可以提高用水效率,减少总体用水量,增强干旱适应能力和整体系统恢复力,提高产量,降低种子、农药、排水和劳动力的生产成本,增加农户收入,提升可持续发展水平[72-75]

最近关于稻田水分管理的研究强调了减少CH4排放的同时提高用水效率的潜力[75],这也体现了业界对于农业生产节水的广泛关切。对人工灌排稻田减排效果的荟萃分析发现,采用干湿交替(AWD)灌溉管理[76]可减少20%~30%的CH4排放量和25.7%的用水量,尽管这在个别情况下会导致产量小幅下降(5.4%)[77],更多研究则发现了与AWD相关的产量提升[75]。实际上,采取中期烤田水分管理方式的稻田,即使在烤田结束覆水后仍能将CH4排放量保持在较低水平[78]。近年来,干湿交替灌溉技术在东南亚为主的水稻主产区推广[79],实现了良好的增产减排效果。基于干湿交替灌溉技术的良好应用前景,更加需要量化该技术对区域的适用性程度,以提高其应用范围。与连续淹灌相比,越南的AWD被发现分别减少了29%~30%的CH4和26%~27%的氧化亚氮(N2O)排放量,净温室效应的减排率约为30%[75]。然而,如果同时考虑CH4和N2O的减排,水分管理的优化可能会对二者产生相反的效应(trade off),因为干湿交替灌溉会增加N2O排放[75]。研究表明,与持续淹水相比较,中期烤田可以将稻田CH4排放总量显著降低36%~77%[80-81],但可能导致N2O排放量增加约20%[82];据测算,单次和多次排水的N2O排放量变化范围为0.06~33 kg/hm2[83-84],N2O的排放量在旱季较高[82],这取决于特定地点的因素以及投入水稻系统的化肥和有机物质的数量。AWD技术在部分地区的推广,是建立在综合温室效应(↓CH4+↑N2O)减缓的基础上,毕竟稻田温室效应主要由CH4贡献(90%以上),这种情况下,N2O排放的增加就不能掩盖AWD技术的减排效果了。尽管如此,包括AWD在内的节水减氮措施在实际执行中还存在一些障碍,主要包括土壤类型、渗透率或降水波动、水渠或灌溉基础设施、稻田地表水平和稻田面积的特定区域限制,以及社会因素,包括农民的看法、水泵所有权和同步方面的挑战,邻居和泵站之间的水资源管理等问题[74,85],只有全面权衡社会效益和经济效益的减排措施才能更广泛地被接受。

全球碳中和背景下温室气体减排已成为国际共识,如2021年中美两国发布《格拉斯哥联合宣言》,表明了两国和国际社会共同致力于CH4减排的努力。但如何在确保粮食和重要农产品有效安全供给的前提下,实现稻田CH4减排,仍需在宏观政策和针对性技术上加强顶层设计和减排技术适用性评估。目前,针对AWD技术的大范围区域适用性评估,国际水稻研究所开展了系列研究。如Sander等[86]基于Nelson等[87]的理论并结合IPCC Tier 2算法[88],评估了菲律宾全国稻田AWD技术适用性,其结果与Nelson等[87]的研究相似,即降雨较少的水稻种植季AWD技术适用性更高。Prangbang等[89]则评估了泰国中部平原6个水稻省份AWD技术适用性,他们针对不同土壤质地设置了不同的土壤渗透率,一定程度上影响了中度及高度适宜区域的分布;且长期种植水稻的土壤表层会形成“硬块”,这种“硬块”会影响土壤渗透率,进而影响评估结果。另外,由于地势较高的稻田往往比地势低的稻田更容易排水,从而影响该技术的适用性[74]。实际上,不止节水措施,考虑到稻米供给的前提和地理位置、气候和土壤属性等的较大差异,上述提到的所有稻田减排措施的推广都需要进行适用性评估,目前这种评估还相对滞后。

减投增效,一方面在于控制水肥投入抑制CH4产生,更重要的还在于通过水肥耕作等的高效耦合提质增效。刘天奇等[35]发现,节水灌溉技术可通过激活甲烷氧化菌丰度,减少稻田CH4排放19.9%~21.1%;免耕等低能耗管理则可减少燃油和人力等投入,综合降低稻田生产间接碳排放10.5%~16.7%;而相对于常规稻草还田,节水灌溉结合氮肥配施等实践可提高稻草外源碳循环固定率57.3%~59.9%。最新研究发现,通过水稻氮素响应染色质调控等位基因编码(NGR5),实现分蘖与施肥脱钩,在减少氮肥用量的同时,可抑制分蘖期的CH4高排放,并提高水稻产量[90],这种产量和投入的变化可以促进农业可持续性和粮食安全。传统上,我们更习惯使用尿素,实际上,氮肥和CH4循环的相互作用是复杂的,在不同的组织层次上会产生不同的影响。但Bodelier等[91]通过测量所涉及的反应速率、稳定同位素示踪和土壤中细菌群落的分子分析,发现相比尿素,铵基肥料能更大程度刺激水稻根围甲烷氧化菌的生长和活性。Shrestha等[92]也发现,硫酸铵强烈抑制CH4生成,该处理中,II型甲烷氧化菌相对更占优势。除了新型氮肥,包膜控释肥已经在旱作系统中成功应用于抑制N2O的排放,但在稻田中对CH4的抑制效应仍在探索。Hou等[93]发现,硫包膜尿素与普通尿素长期配施可保持水稻产量并减少稻田CH4排放。Scholz等[94]也认为硫酸盐还原剂和产甲烷菌竞争相同的底物,所以硫酸盐修正是一种减少稻田CH4排放的缓解策略,而通过电硫化物氧化增加硫酸盐水平的丝状细菌(电缆细菌)的一次性接种,会使硫酸盐库存增加5倍,从而导致CH4排放量减少93%。

综上所述,稻田CH4减排涉及稻米供应、气候适应及土地可持续生产,需构建综合技术体系才能实现减排增产的多目标协同。需综合考虑气候变化不利影响、固碳减排丰产难兼顾、低碳品种和农艺农机不同步及水热气候资源不匹配等重大问题,通过互作机制、关键技术和主产区针对性协同增效模式的创新研发,建立主产稻区适用的 “抑菌减排-增腐固碳-良种丰产-减投增效”的“抑增良减”技术体系(图3)。

图3

图3   稻田CH4减排“抑增良减”技术体系

Fig. 3   CH4 emission reduction technology system of “suppressing, increase, improving & reduction” in paddy fields


3 水稻低碳生产战略路径

我国是受气候变化不利影响较严重的国家,同时也是世界范围内稻米及粮食安全的重要保障国。应对气候变化不利影响和保证稻米稳定安全供给,是水稻低碳生产战略转型的两大前提,低碳技术模式的应用必须同时受这两大前提约束。因此,本部分在综述未来气候变化对水稻生产潜在影响的基础上,提出了应对气候变化的主产区减排技术模式,从而提出以食物系统视角的水稻低碳生产战略路径。

3.1 未来气候变化对水稻生产的潜在影响

《中国气候与生态环境演变报告》[95]指出,1900—2018年,中国增温比全球平均更快,1961—2013年达1.44℃(1.22~1.66℃),1961—2020年,中国平均地面气温呈上升趋势,区域差异明显,北方高于南方。其中1961—2010年的气温升高使我国单季稻产量增加了11%,降水变化使单季稻产量增加了6.2%,同时使我国水稻产量重心向东北迁移了约3个纬度。我国整体气候变化还表现为强降水、极端高温-高湿复合事件大幅增加及光热资源减少等特征。与此同时,我国中东部地区耕地面积有减少的趋势。水稻种植比例结构的变化在南北方呈相反的趋势,其中东北稻作面积增加明显。而全国单作面积减少导致水稻产量下降4.3%~12.4%[95]。另外,气候变化对水稻播期的影响则是出现了春播提前秋播推迟的现象。对于农业受气候变化影响程度及敏感程度而言,各地区也有较大差异,其中东北、华中和西南地区受影响和敏感程度均最高,华东地区则是农业受影响程度较大但敏感度较低,而华南地区农业敏感性较高。我国水稻目前有四大主产区,分别是长江中下游、东北平原、华南和西南地区。《中国气候与生态环境演变报告》[95]数据表明,未来我国水稻将在温度、降水、干旱发生频次和强度及种植结构等方面发生较大变化,并且四大主产区将分别面临不同的变化特征(表2)。针对这种全球变暖影响下的水稻生产将发生的变化,可持续水稻生产措施和绿色低碳转型政策技术体系既要同时做到科学性和前瞻性,又要充分考虑应对气候变化不利影响,制定区域针对性减排增效模式。

表2   我国气候变化特征及其对水稻产量、耕地面积和种植结构的影响[95]

Table 2  Characteristics of climate change in China and its impact on rice yield, cultivated land area and planting structure [95]

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3.2 应对气候变化的主产区减排技术模式

长江中下游是我国最主要的稻谷产区,针对未来气候变化潜在影响,实施“抑增良减”技术体系:在抑菌减排层面,该地区特别是下游稻麦轮作区,适于实施控水增氧-联合菌剂产品;同时考虑增腐固碳,可实行快腐菌剂-轮作-高效机具的技术措施;该地区水稻品种更替也较快,适宜播种超级杂交稻等优质品种提升产量的同时降低CH4排放;最后,针对减投增效,适宜实施化肥减量-新型肥料制剂-绿肥覆盖作物的种植体系。

华南和西南是传统稻作区。华南是典型的双季稻三季稻种植区,适宜推广秸秆腐熟-覆盖作物-超短生育期高成穗率低排品种-减肥-生物质炭的热区减排增效技术模式。西南稻区地处长江上游,多种植一季稻,常见稻麦轮作和稻菜轮作系统,适宜推广冬季覆盖作物-低碳品种-覆膜保墒等针对性技术措施。东北地区是目前增速较快的单季粳稻主产区,特别是黑龙江省,水稻种植面积已经超过江西省,成为全国仅次于湖南的第二水稻种植大省。针对低温和水资源紧缺的问题,东北主产区易采用寒地秸秆快速腐熟深埋还田-优质高产粳稻品种-节水-覆膜保墒的绿色低碳增效技术体系。

3.3 水稻低碳转型多目标调控途径

水稻是我国粮食供给系统的支柱产业,以国家粮食安全和大食物观的视角出发,水稻生产低碳转型是一项复杂的系统工程。自IPCC第五次评估报告发布以来,稻田CH4减排研究主要集中在水分和养分管理实践上,目的是提高水稻生产可持续性以及特定区域排放量的估算,因而相关研究结果显示出相当大的空间和时间变化,这取决于特定区域的因素,包括土壤有机质的变化、田间水分的管理、施肥的类型和数量、水稻品种及当地耕作方式。实际上,我国水稻生产系统仍然面临碳汇功能不强、CH4排放强度大、固碳减排难兼顾等问题,因此,稻田CH4减排技术研发不是单一问题,需要面对稻田固碳减排、生态功能提升和丰产增效的多目标调控需求。这需要在单项减排技术基础上,集成CH4排放、水稻丰产和土壤碳汇的互作效应及其调控技术途径,优化多种技术措施组合,包括高产低排水稻品种筛选、秸秆催腐、CH4氧化、水旱轮耕等关键技术与产品研制,还需结合稻田秸秆还田、土壤耕作、水肥调控等绿色增汇丰产栽培技术模式,从而创建适于我国主要水稻产区稻田碳汇提升与CH4低排放的技术体系。

面对未来气候变化影响、稻米供应和减排增碳的多重需求,我国水稻低碳生产战略的实施需要综合考虑人为强化措施的干预和基于自然的解决方案(图4)。其中人为强化措施包括品种选育、灌溉-施肥-耕作优化、菌剂产品和高效机具的联合研发。基于自然的解决方案则主要包括绿肥种植、多种轮作系统提升生物多样性等作物综合管理和水稻集约化系统。其中人为强化措施是满足粮食和重要农产品稳定安全供给战略需求下,提升水稻生产力和减排固碳所必须采取的措施;而基于自然的解决方案则是在碳达峰碳中和背景下,提升碳汇和生态功能,增加可持续发展水平的保证。

图4

图4   水稻低碳生产战略路径桑基图

注:调控方案分为人为强化和基于自然的解决方案2大类9小类,互作效应表明9个小类调控手段之间的交互,技术手段则是在9小类措施下的具体技术模式及其组合,调控途径则表示从技术手段到调控目标路径,其中也包括诸多技术的交互调控机制。

Fig. 4   Sankey diagram of rice low-carbon production strategic path


4 结论和展望

CH4减排涉及产生、氧化和传输全过程调控,而这些过程又与水稻栽培措施和生长特性紧密相关,同时,土壤属性、气候要素以及未来气候变化等因素都会对稻田CH4减排技术的发展、政策措施的制定产生影响。更重要的是,我国是世界第二人口大国,确保稻米等主粮作物自给率稳定在95%红线以上,保障粮食等重要农产品稳定安全供给仍然是农业生产的首要任务。因此,稻田CH4减排要以丰产增效为核心目标,融合人为和自然两种强化和调控手段,充分考虑并挖掘“植株-土壤-微生物”“固碳减排-绿色投入-污染防控”及“CH4减排-碳库扩容-生态功能提升”三类互作效应。系统实施水、肥、苗、耕、机具产品等低碳运筹,集成主产区“抑菌减排-增腐固碳-良种丰产-减投增效”技术体系。在此基础上,实施覆盖作物种植、免耕轮作、高产低排品种选育、覆膜保墒、菌剂增效产品、智能机具、合理密植、肥蘖脱钩、干湿交替和增氧耕作等十大技术模式。与此同时,充分考虑未来气候变化的可能影响,推广区域针对性适应与减缓协同技术,构建气候智慧型丰产增效水稻生产体系(图5)。

图5

图5   气候智慧型水稻减排增效生产体系

Fig. 5   Climate-smart rice production system with emission reduction and efficiency enhancement


CH4减排是当前国际气候变化领域的重点关切,2021年底,中美签署格拉斯哥联合宣言,两国将就农业在内的多个部门联手开展CH4管控工作,同时,全球甲烷宣言、全球甲烷中心和全球甲烷行动等国际倡议相继被发起,但这些倡议都为发达国家主导,如何参与,如何制定减排技术和政策,我们更要以中国国情为基础。我国超过60%的人口以大米为主食,因此,稻米品质提升和有效供给是水稻低碳生产战略转型的首要前提。我国稻谷单产连年提升的同时,仍然存在丰产固碳不同步、减排增效难兼顾等问题,此外,稻田CH4全过程调控领域还存在一定知识差距,减排增碳丰产增效的碳氮调控、分子生物学、稳定同位素和深度学习及人工智能辅助等重大基础理论仍有待突破,而减排固碳措施的成本效益评估也相对滞后,一定程度上限制了技术措施的推广应用。因此,未来稻田CH4减排应建立“重大理论突破—减排技术研发—成本效益评估—模式集成示范”的研发体系,以高效基础和应用研究推进我国水稻低碳转型和农业绿色高质量发展。

参考文献

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Submerged rice paddy soils are the major anthropogenic source of methane (CH ) emission to the atmosphere. Straw incorporation for sustaining soil organic C pool increases CH emission flux from rice paddy soils. Though the rate of nitrous oxide (N O) emission is much less than CH, the former has 298 times higher global warming potential (GWP) than equivalent quantity of carbon dioxide. The effect of chelating agents, such as EDTA, on N O emission and on GWP due to CH and N O emissions has not been evaluated before.The emission of CH gas from submerged soil may be mitigated by EDTA application; however, it also increases concentration of nitrate-N in soil, the precursor of N O gas formation under anaerobic condition. In this experiment, irrespective of straw application, EDTA-treated soils emitted less CH to the atmosphere than the corresponding control. Though N O emission was increased from soil due to EDTA applications, total GWP was at least 15% reduced in EDTA treated soils during rice cultivation. The plant growth and rice grain yield was not affected by EDTA application.EDTA application at 5.0 ppm might be used to reduce total global warming potential during rice cultivation. © 2016 Society of Chemical Industry.© 2016 Society of Chemical Industry.

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【目的】稻田生态系统的温室气体排放一直是气候变化领域的研究热点,对发展低碳农业和缓解全球变暖具有重要意义。研究控释肥和添加剂对双季稻(Oryza sative L)温室气体排放和产量的影响,旨在综合评价其减排效果,筛选既能保证产量又能有效减排的施肥措施。【方法】以华中江汉平原地区双季稻为研究对象,设置6种不同控释肥或添加剂处理,包括①习惯施肥作为对照,②硫包膜控释尿素,③树脂包膜控释尿素,④缓释碧晶尿素,⑤尿素中加入质量分数1%的硝化抑制剂二甲基吡唑磷酸盐(DMPP),⑥施肥时泼洒与尿素等量的1:200倍稀释有效微生物菌剂培养液(EM菌剂),采用自动静态箱-气相色谱法对温室气体排放通量进行长期连续监测,同步观测土壤无机氮素和产量,得出不同施肥处理的温室气体(CH4和N2O)排放特征,由内插加权法求得排放总量,最终计算出综合温室效应和排放强度。【结果】不同施肥处理下CH4和N2O排放通量具有较为明显的季节变化规律。早稻CH4排放总量以树脂包膜控释尿素最低,晚稻以碧晶尿素最低;而早稻和晚稻N2O排放总量均以硝化抑制剂DMPP最低。综合两个季节,各施肥处理的综合温室效应(以CO2当量100年算)差异显著(P<0.05),其中常规施肥>硫包膜控释尿素>硝化抑制剂DMPP>EM菌剂>碧晶尿素>树脂包膜控释尿素;控释肥和添加剂处理对比常规均有不同程度的减排效果,其中树脂包膜控释尿素减排效果最高为56.2%,碧晶尿素次之为45.6%,且晚稻减排效果明显高于早稻。早稻控释肥和添加剂处理产量与常规施肥差异不显著,晚稻则存在显著增产,增产幅度为13.5%—16.2%。各处理的温室气体排放强度GHGI以树脂包膜控释尿素最低,与常规施肥差异极显著(P<0.01)。【结论】双季稻不同施肥处理CH4和N2O的排放总量差异显著,控释肥和添加剂处理均能达到不同程度的减排。控释肥和添加剂处理对早稻增产效果差异不显著,对晚稻增产效果差异显著,减排效果也高于早稻。综合考虑经济效益和减排效果,可得出在当前的稻田管理条件下施用包膜控释肥、抑制剂和生物菌剂,能保证产量并有效降低温室气体排放,是水稻低碳高产可行的施肥措施。

Wang B, Li Y E, Wan Y F, et al.

Effect and assessment of controlled release fertilizer and additive treatments on greenhouse gases emission from a double rice field

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【Objective】It is well known that the issue of greenhouse gases (GHGs) emission from rice ecosystem has been concerned within the scope of climate change research over years. The effect of controlled release fertilizer and additive treatments on GHGs emission and rice yield in a double rice (Oryza sative L) field was investigated to evaluate their potential of GHGs reduction and yield promotion, this study is also very important for the development of low-carbon agriculture and the mitigation research of global warming.【Method】Taking the double rice in Jianghan Plain, Hubei province, Central China as the object, a continuous observation of greenhouse gas emission from six different controlled release fertilizer or additive treatments (CK: conventional urea, CRU1: sulfur-coated urea, CRU2: polymer-coated urea, CU: nitrapyrin crystal urea, DMPP: nitrification inhibitor, EM: effective microorganisms) was conducted by using the automatic static chamber-GC (gas chromatography) method, the rice yield and soil properties were also monitored simultaneously. Variation and characterization of GHGs (CH4 and N2O) emission, greenhouse effect (CO2-e) and greenhouse gas intensity of each treatment were analyzed comprehensively.【Result】The results indicated that CH4 and N2O emission in different fertilizer treatments had an obvious daily and seasonal variation law in double rice ecosystem. Controlled release urea (polymer-coated) caused the lowest CH4 emission during the early rice, while the nitrapyrin crystal urea had the lowest CH4 emission during the late rice growing season. In consideration of N2O, the DMPP had the lowest emission during the two rice growing season compared to the other field applications. Pronounced differences were discovered among 6 treatments on global greenhouse effect (CO2-e,on 100 a horizon) during the whole rice growing season (P<0.05). Among the field applications, CRU1 had the lowest global greenhouse effect, followed by CU, EM, DMPP, CRU2, and CK, respectively. Furthermore, significant greenhouse effect reduction potential was also employed; the polymer-coated urea dominated the fashion with the highest reduction potential of 56.2% compared to traditional fertilization, followed by nitrapyrin crystal urea (45.6%). In the view of rice yield, five other treatments were significantly higher than CK during late rice (stimulated rice yield by 13.5%-16.2%) while no statistical differences were found during early rice. Additionally, GHGI of polymer-coated urea was statistically lower than the other applications including the conventional fertilization (P<0.01). 【Conclusion】Various reduction potential and yield promotion effects existed among different field applications from the double rice cropping system, this influence was significant during the late rice growing season but not remarkable in the early rice,while synthetically consideration of their economic earnings and environmental effects, the application of controlled release urea benefitted the most to the rice production, followed by nitrification inhibitor and biopreparate under the current field management conditions.

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[J]. 植物营养与肥料学报, 1999 (1): 94-97.

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Xu Y C, Wang Z Y, Li Z, et al.

Effect of rice cultivars on methane emission from Beijing rice field

[J]. Plant Nutrition and Fertilizer Science, 1999 (1): 94-97 (in Chinese)

[本文引用: 1]

Aulakh M S, Bodenbender J, Wassmann R, et al.

Methane transport capacity of rice plants. II. Variations among different rice cultivars and relationship with morphological characteristics

[J]. Nutrient Cycling in Agroecosystems, 2000, 58 (1-3): 367-375

DOI:10.1023/A:1009839929441      URL     [本文引用: 1]

Khosa M K, Sidhu B S, Benbi D K.

Effect of organic materials and rice cultivars on methane emission from rice field

[J]. Journal of Environmental Biology, 2010, 31 (3): 281-285

PMID:21046997      [本文引用: 1]

A field experiment was conducted for two years on a sandy loam (Typic Ustochrept) soil of Punjab to study the effect of organic materials and rice cultivars on methane emission from rice fields. The methane flux varied between 0.04 and 0.93 mg m(-2) hr(-1) in bare soil and transplanting of rice crop doubled the methane flux (0.07 to 2.06 mg m(-2) hr(-1)). Among rice cultivars, significantly (p < 0.05) higher amount of methane was emitted from Pusa 44 compared to PR 118 and PR 111. Application of organic materials enhanced methane emission from rice fields and resulted in increased soil organic carbon content. The greatest seasonal methane flux was observed in wheat straw amended plots (229.6 kg ha(-1)) followed by farmyard manure (111.6 kg ha(-1)), green manure (85.4 kg ha(-1)) and the least from rice straw compost amended plots (36.9 kg ha(-1)) as compared to control (21.5 kg ha(-1)). The differential effect of organic materials in enhancing methane flux was related to total carbon or C:N ratio of the material. The results showed that incorporation of humified organic matter such as rice straw compost could minimize methane emission from rice fields with co-benefits of increased soil fertility and crop productivity.

Singh S, Kumar S, Jain M C.

Methane emission from two Indian soils planted with different rice cultivars

[J]. Biology and Fertility of Soils, 1997, 25 (3): 285-289

DOI:10.1007/s003740050316      URL     [本文引用: 1]

江瑜, 管大海, 张卫建.

水稻植株特性对稻田甲烷排放的影响及其机制的研究进展

[J]. 中国生态农业学报, 2018, 26 (2): 175-181.

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Jiang Y, Guan D H, Zhang W J.

The effect of rice plant traits on methane emissions from paddy fields: a review

[J]. Chinese Journal of Eco-Agriculture, 2018, 26 (2): 175-181 (in Chinese)

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Adviento-Borbe M A, Pittelkow C M, Anders M, et al.

Optimal fertilizer nitrogen rates and yield-scaled global warming potential in drill seeded rice

[J]. Journal of Environmental Quality, 2013, 42 (6): 1623-1634

DOI:10.2134/jeq2013.05.0167      PMID:25602403      [本文引用: 1]

Drill seeded rice ( L.) is the dominant rice cultivation practice in the United States. Although drill seeded systems can lead to significant CH and NO emissions due to anaerobic and aerobic soil conditions, the relationship between high-yielding management practices, particularly fertilizer N management, and total global warming potential (GWP) remains unclear. We conducted three field experiments in California and Arkansas to test the hypothesis that by optimizing grain yield through N management, the lowest yield-scaled global warming potential (GWP = GWP Mg grain) is achieved. Each growing season, urea was applied at rates ranging from 0 to 224 kg N ha before the permanent flood. Emissions of CH and NO were measured daily to weekly during growing seasons and fallow periods. Annual CH emissions ranged from 9.3 to 193 kg CH-C ha yr across sites, and annual NO emissions averaged 1.3 kg NO-N ha yr. Relative to NO emissions, CH dominated growing season (82%) and annual (68%) GWP. The impacts of fertilizer N rates on GHG fluxes were confined to the growing season, with increasing N rate having little effect on CH emissions but contributing to greater NO emissions during nonflooded periods. The fallow period contributed between 7 and 39% of annual GWP across sites years. This finding illustrates the need to include fallow period measurements in annual emissions estimates. Growing season GWP ranged from 130 to 686 kg CO eq Mg season across sites and years. Fertilizer N rate had no significant effect on GWP; therefore, achieving the highest productivity is not at the cost of higher GWP. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Pittelkow C M, Adviento-Borbe M A, Hill J E, et al.

Yield-scaled global warming potential of annual nitrous oxide and methane emissions from continuously flooded rice in response to nitrogen input

[J]. Agriculture Ecosystems & Environment, 2013, 177: 10-20

DOI:10.1016/j.agee.2013.05.011      URL     [本文引用: 1]

Lueke C, Bodrossy L, Lupotto E, et al.

Methanotrophic bacteria associated to rice roots: the cultivar effect assessed by T-RFLP and microarray analysis

[J]. Environmental Microbiology Reports, 2011, 3 (5): 518-525

DOI:10.1111/j.1758-2229.2011.00251.x      PMID:23761330      [本文引用: 1]

Rice plants play a key role in regulating methane emissions from paddy fields by affecting both underlying processes: methane production and oxidation. Specific differences were reported for methane oxidation rates; however, studies on the bacterial communities involved are rare. Here, we analysed the methanotrophic community on the roots of 18 different rice cultivars by pmoA-based terminal restriction fragment length polymorphism (T-RFLP) and microarray analysis. Both techniques showed comparable and consistent results revealing a high diversity dominated by type II and type Ib methanotrophs. pmoA microarrays have been successfully used to study methane-oxidizing bacteria in various environments. However, the microarray's full potential resolving community structure has not been exploited yet. Here, we provide an example on how to include this information into multivariate statistics. The analysis revealed a rice cultivar effect on the methanotroph community composition that could be affiliated to the plant genotype. This effect became only significant by including the specific phylogenetic resolution provided by the microarray into the statistical analysis.© 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

Liechty Z, Santos-Medellin C, Edwards J, et al.

Comparative analysis of root microbiomes of rice cultivars with high and low methane emissions reveals differences in abundance of methanogenic archaea and putative upstream fermenters

[J]. mSystems, 2020, 5(1)

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Serrano-Silva N, Valenzuela-Encinas C, Marsch R, et al.

Changes in methane oxidation activity and methanotrophic community composition in saline alkaline soils

[J]. Extremophiles, 2014, 18 (3): 561-571

DOI:10.1007/s00792-014-0641-1      PMID:24638260      [本文引用: 1]

The soil of the former Lake Texcoco is a saline alkaline environment where anthropogenic drainage in some areas has reduced salt content and pH. Potential methane (CH4) consumption rates were measured in three soils of the former Lake Texcoco with different electrolytic conductivity (EC) and pH, i.e. Tex-S1 a >18 years drained soil (EC 0.7 dS m(-1), pH 8.5), Tex-S2 drained for ~10 years (EC 9.0 dS m(-1), pH 10.3) and the undrained Tex-S3 (EC 84.8 dS m(-1), pH 10.3). An arable soil from Alcholoya (EC 0.7 dS m(-1), pH 6.7), located nearby Lake Texcoco was used as control. Methane oxidation in the soil Tex-S1 (lowest EC and pH) was similar to that in the arable soil from Alcholoya (32.5 and 34.7 mg CH4 kg(-1) dry soil day(-1), respectively). Meanwhile, in soils Tex-S2 and Tex-S3, the potential CH4 oxidation rates were only 15.0 and 12.8 mg CH4 kg(-1) dry soil day(-1), respectively. Differences in CH4 oxidation were also related to changes in the methane-oxidizing communities in these soils. Sequence analysis of pmoA gene showed that soils differed in the identity and number of methanotrophic phylotypes. The Alcholoya soil and Tex-S1 contained phylotypes grouped within the upland soil cluster gamma and the Jasper Ridge, California JR-2 clade. In soil Tex-S3, a phylotype related to Methylomicrobium alcaliphilum was detected.

Su J, Hu C, Yan X, et al.

Expression of barley SUSIBA2 transcription factor yields high-starch low-methane rice

[J]. Nature, 2015, 523 (7562)

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Du L, Wang Y F, Shan Z, et al.

Comprehensive analysis of SUSIBA2 rice: the low-methane trait and associated changes in soil carbon and microbial communities

[J]. Science of The Total Environment, 2021, 764

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Soremi P A S, Chirinda N, Graterol E, et al.

Potential of rice (Oryza sativa L.) cultivars to mitigate methane emissions from irrigated systems in Latin America and the Caribbean

[J]. All Earth, 2023, 35 (1): 149-157

DOI:10.1080/27669645.2023.2207941      URL     [本文引用: 1]

Minami K.

Atmospheric methane and nitrous oxide: sources, sinks and strategies for reducing agricultural emissions

[J]. Nutrient Cycling in Agroecosystems, 1997, 49 (1-3): 203-211

DOI:10.1023/A:1009730618454      URL     [本文引用: 1]

Yu K W, Wang Z P, Chen G X.

Nitrous oxide and methane transport through rice plants

[J]. Biology and Fertility of Soils, 1997, 24 (3): 341-343

DOI:10.1007/s003740050254      URL     [本文引用: 1]

Mosier A R, Mohanty S K, Bhadrachalam A, et al.

Evolution of dinitrogen and nitrous oxide from the soil to the atmosphere through rice plants

[J]. Biology and Fertility of Soils, 1990, 9 (1): 61-67

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Schütz H, Holzapfel-Pschorn A, Conrad R, et al.

A 3-year continuous record on the influence of daytime, season, and fertilizer treatment on methane emission rates from an Italian rice paddy

[J]. Journal of Geophysical Research: Atmospheres, 1989, 94 (D13): 16405-16416

DOI:10.1029/JD094iD13p16405      URL     [本文引用: 1]

CH4 emission rates have been measured in an Italian rice paddy between 1984 and 1986, covering three vegetation periods. For these measurements a fully automated, computerized sampling and analyzing system was developed which allowed the simultaneous determination of CH4 emission rates at 16 different field plots. CH4 emission rates showed strong diurnal and seasonal variations. Diurnal changes correlated with changes in soil temperature. During the season, CH4 emission rates showed a first maximum in May–June before tillering and a second maximum in July during the reproductive stage of the rice plants. In 1985 and 1986 two maxima were observed during summer in addition to the first maximum in the rate of CH4 emission during spring. Application of mineral and/or organic fertilizer strongly influenced the CH4 emission rates, depending on the type, rate, and mode of fertilizer application. Thus the rates decreased by at most 40% and 60% after fertilization by deep incorporation with 200 kg N/ha urea and 200 kg N/ha ammonium sulfate, respectively. Application of 200 kg N/ha calcium cyanamide led to a reduction of the first maximum of CH4 emission but caused the second maximum to increase, the overall result being that the seasonally averaged CH4 emission rate was comparable to that observed in unfertilized fields. Application of rice straw at a rate of 12 t/ha enhanced the rate of CH4 emission by a factor of 2 compared with the control. Higher application rates of rice straw did not cause a further increase in CH4 emission. The complete records of CH4 emissions over three vegetation periods indicate an average seasonal CH4 emission rate from unfertilized fields of 0.28 g CH4/m2 d, with a range of 0.16–0.38 g CH4/m2 d. Based on this value and applying the observed temperature dependence of the CH4 emission rates, the global annual CH4 emission from rice paddies is estimated to be in the range of 50–150 Tg, with a likely average of 100 Tg. This figure represents between 19% and 25% of the global CH4 emission, indicating that rice paddies are one of the most important individual sources of atmospheric CH4.

Tyler S C, Bilek R S, Sass R L, et al.

Methane oxidation and pathways of production in a Texas paddy field deduced from measurements of flux, delta δ13C, and δD of CH4

[J]. Global Biogeochemical Cycles, 1997, 11 (3): 323-348

DOI:10.1029/97GB01624      URL     [本文引用: 1]

Irrigated rice paddies are one of the few methane (CH4) sources where the management of its emissions may be possible. Before that can be initiated, however, the relationship between production, oxidation, and emission of CH4 and the processes controlling them must be better known. To that end we have made measurements of concentration and stable carbon and hydrogen isotopes of CH4 and CO2 in paddy fields along the Gulf Coast of Texas. Although only small differences in total CH4 flux (∼46.5 g m-2 clayey and ∼43 g m-2 sandy) and average δ13CH4 (seasonal averages of -56.11±1.21‰ clayey and -53.57±0.97‰ sandy) from emitted CH4 were observed in two plots with different soil textures, by making additional measurements of belowground CH4 and CO2 we learned much about processes occurring in the paddy field. We estimated that roughly 98% of the CH4 released was transported through the plant and that residence times for belowground CH4 were from about 1 to 5 hours during most of the season, indicating fast processing of both organic carbon and current photosynthesized carbon to make CH4. The percentage of CH4 made from acetate fermentation calculated using isotope data was strongly dependent on the value of the fractionation factor (α) associated with the CO2/H2 reduction pathway for CH4 formation. Using a range of reasonable values for α, we calculated that acetate fermentation was from 67 to 80% early in the season to 29 to 60% late in the season (generally decreasing as the season progressed). Most importantly, we have strong evidence that rhizospheric CH4 oxidation occurs in paddy fields. We have developed a semiempirical equation and used it to calculate the percent of CH4 oxidized as a function of total CH4 produced from field measurements of δ13CH4 under natural conditions. Because most emitted CH4 is transported by the rice plant, it was necessary to determine the isotopic fractionation CH4 underwent during its transport through the plant. This value, 12±l‰, was used to calculate oxidation percent using belowground and emitted δ13CH4 values. In Texas, oxidation of CH4 in the soil increased from ∼20 to ∼60% over the 6 week period just prior to harvest.

Chen Y, Li S Y, Zhang Y J, et al.

Rice root morphological and physiological traits interaction with rhizosphere soil and its effect on methane emissions in paddy fields

[J]. Soil Biology and Biochemistry, 2019, 129: 191-200

DOI:10.1016/j.soilbio.2018.11.015      URL     [本文引用: 1]

Kim W J, Bui L T, Chun J B, et al.

Correlation between methane (CH4) emissions and root aerenchyma of rice varieties

[J]. Plant Breeding and Biotechnology, 2018, 6 (4): 381-390

DOI:10.9787/PBB.2018.6.4.381      URL     [本文引用: 1]

Avnery S, Mauzerall D L, Fiore A M.

Increasing global agricultural production by reducing ozone damages via methane emission controls and ozone-resistant cultivar selection

[J]. Global Change Biology, 2013, 19 (4): 1285-1299

DOI:10.1111/gcb.12118      PMID:23504903      [本文引用: 1]

Meeting the projected 50% increase in global grain demand by 2030 without further environmental degradation poses a major challenge for agricultural production. Because surface ozone (O3 ) has a significant negative impact on crop yields, one way to increase future production is to reduce O3 -induced agricultural losses. We present two strategies whereby O3 damage to crops may be reduced. We first examine the potential benefits of an O3 mitigation strategy motivated by climate change goals: gradual emission reductions of methane (CH4 ), an important greenhouse gas and tropospheric O3 precursor that has not yet been targeted for O3 pollution abatement. Our second strategy focuses on adapting crops to O3 exposure by selecting cultivars with demonstrated O3 resistance. We find that the CH4 reductions considered would increase global production of soybean, maize, and wheat by 23-102 Mt in 2030 - the equivalent of a ~2-8% increase in year 2000 production worth $3.5-15 billion worldwide (USD2000 ), increasing the cost effectiveness of this CH4 mitigation policy. Choosing crop varieties with O3 resistance (relative to median-sensitivity cultivars) could improve global agricultural production in 2030 by over 140 Mt, the equivalent of a 12% increase in 2000 production worth ~$22 billion. Benefits are dominated by improvements for wheat in South Asia, where O3 -induced crop losses would otherwise be severe. Combining the two strategies generates benefits that are less than fully additive, given the nature of O3 effects on crops. Our results demonstrate the significant potential to sustainably improve global agricultural production by decreasing O3 -induced reductions in crop yields.© 2012 Blackwell Publishing Ltd.

Wang B, Neue H U, Samonte H P.

Effect of cultivar difference ('IR72', 'IR65598' and 'Dular') on methane emission

[J]. Agriculture Ecosystems & Environment, 1997, 62 (1): 31-40

DOI:10.1016/S0167-8809(96)01115-2      URL     [本文引用: 1]

Setyanto P, Kartikawati R.

Integrated rice crop management for low emitance of methane

[J]. Indonesian Journal of Agriculture, 2011, 4 (1): 8-16

[本文引用: 2]

Nihayah B, Nugroho B D A, Hasanah N A I, et al.

Methane (CH4) emission flux estimation in SRI (system of rice intensification) method rice cultivation using different varieties and fertilization

[J]. IOP Conference Series: Earth and Environmental Science, 2021, 757 (1): 012001

DOI:10.1088/1755-1315/757/1/012001      [本文引用: 1]

The agricultural sector is one of the contributors of the greenhouse gasses emission especially CO2, CH4 and N2O. In its agricultural practice, rice paddy fields in Indonesia is cultivated twice to three times a year. Conventional rice planting method using water inundation and chemical fertilizer can result in the increase of greenhouse gasses emission. One of those gasses is methane (CH4). Methane is formed through the decomposition of organic materials anaerobically in the rhizosphere with the help of methanogenic microbes. The release of methane can be influenced by several factors among them are the nature of the soil, irrigation system, fertilization and varieties used. The strategy to reduce emission conducted in this research are the usage of varieties that are considered to be low on methane emission such as Ciherang and IR64, rice paddy cultivation SRI (System of Rice Intensification) method using intermittent irrigation as well as fertilization. The setting of the intermittent irrigation uses IoT based (Internet of Thing) sensor technology for water level adjustment. The aim of this research is to analyze the methane flux produced from SRI method rice paddy cultivation based on the varieties used and different kinds of fertilization.

Li T Y, Zhang W F, Cao H B, et al.

Region-specific nitrogen management indexes for sustainable cereal production in China

[J]. Environmental Research Communications, 2020, 2 (7): 075002

DOI:10.1088/2515-7620/aba12d      [本文引用: 1]

Effective policy measures are required to control environmental problems caused by nitrogen (N) fertilizer use in intensive crop production systems in China. However, simply reducing the use of N fertilizer in all regions may be detrimental to food security. Here we reviewed N management policies and indicators, with a particular focus on European Union (EU), and designed an N index system for cereal crops in China. We suggest to use N surplus as an (environmental) evaluation index and N input as a guide to meet the dual challenge of food security and environmental sustainability, and propose crop and region-specific standards for these indexes. We inferred a mean critical N surplus of 75 kg N ha-1 for maize, 40 kg N ha-1 for wheat and 70 kg N ha-1 for rice. For N input, Maximum N (Max. N) and Minimum N (Min. N) input indices are proposed, to guide farming practices effectively. Max. N was based on the N demand of crops achieving their potential yield, in different regions, Min. N was based on the N demand of crops at their target yield, while associated N surpluses do not exceed the set critical values. To meet the dual challenge of food security and environmental sustainability, China needs to increase maize and wheat yields by 20%–40% (rice has achieved target yield) while reducing N input by 10%–20%. This requires an enormous increase in N use efficiency. The N management indexes proposed here can be used as benchmarks to monitor the progress at regional level. Max. N and Min. N may have to be updated regularly when potential and target yields, and thereby crop N demand, change. Also, critical N surpluses may have to change when insights in the impacts of these N surpluses change.

Qin X B, Li Y E, Wang B, et al.

Nonlinear dependency of N2O emissions on nitrogen input in dry farming systems may facilitate green development in China

[J]. Agriculture Ecosystems & Environment, 2021, 317: 107456

DOI:10.1016/j.agee.2021.107456      URL     [本文引用: 1]

秦晓波, 李玉娥, 万运帆, .

耕作方式和稻草还田对双季稻田CH4和N2O排放的影响

[J]. 农业工程学报, 2014, 30 (11): 216-224.

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Qin X B, Li Y E, Wan Y F, et al.

Effect of tillage and rice residue return on CH4 and N2O emission from double rice field

[J]. Transactions of the Chinese Society of Agricultural Engineering, 2014, 30 (11): 216-224 (in Chinese)

[本文引用: 1]

秦晓波, 李玉娥, 万运帆, .

免耕条件下稻草还田方式对温室气体排放强度的影响

[J]. 农业工程学报, 2012, 28 (6): 210-216.

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Qin X B, Li Y E, Wan Y F, et al.

Effects of straw mulching on greenhouse gas intensity under on-tillage conditions

[J]. Transactions of the Chinese Society of Agricultural Engineering, 2012, 28 (6): 210-216 (in Chinese)

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秦晓波, 李玉娥, Wang H, .

生物质炭添加对华南双季稻田碳排放强度的影响

[J]. 农业工程学报, 2015, 31 (5): 226-234.

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Qin X B, Li Y E, Wang H, et al.

Impact of biochar amendment on carbon emissions intensity in double rice field in South China

[J]. Transactions of the Chinese Society of Agricultural Engineering, 2015, 31 (5): 226-234 (in Chinese)

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Yamaguchi T, Minh Tuan L, Minamikawa K, et al.

Compatibility of alternate wetting and drying irrigation with local agriculture in An Giang province, Mekong Delta, Vietnam

[J]. Tropical Agriculture and Development, 2017, 61 (3): 117-127

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Sriphirom P, Chidthaisong A, Towprayoon S.

Effect of alternate wetting and drying water management on rice cultivation with low emissions and low water used during wet and dry season

[J]. Journal of Cleaner Production, 2019, 223: 980-988

DOI:10.1016/j.jclepro.2019.03.212      [本文引用: 1]

Alternate wetting and drying (AWD) system is a water management practice of rice cultivation that has been recommended and promoted to replace continuous flooding (CF). AWD could reduce greenhouse gas (GHG) emissions and save water use without compromising rice yields. However, its effects depend on how water level is effectively controlled. This study aims to evaluate GHG emissions, water use and yield of rice cultivation as affected by the implementation of incomplete AWD and complete AWD. Rice (Oryza sativa L.) was transplanted in the experimental field at Ratchaburi province, Thailand under CF and AWD water management. Water management for AWD in wet season was not complete due to the interference of rainfall in the tillering stage, while it was complete in the dry season. Relative to CF, the incomplete AWD reduced CH4 emission by 10.62% but increased N2O emission by 5.94%. The complete AWD reduced CH4 emission by 23.10% but increased N2O emission by 14.79%. Although both AWD systems increased N2O emission, however, their total global warming potentials (GWP) were still lower than CF by 5.32% under incomplete AWD and 10.83% under incomplete AWD. The incomplete AWD and complete AWD used 11.88% and 3.79% less water (irrigation + rainfall) when compared to CF. In terms of rice yield, it was enhanced only under complete AWD by 2.42% through increased number of tillers and panicles. The yield was reduced under incomplete AWD by 9.12%. Complete AWD and incomplete AWD reduced the irrigation water by 4.52% and 16.72%. The water productivity and water scarcity footprint have been reduced in both AWD systems while the carbon footprint was reduced by 13.95% under complete AWD but increased by 3.44% under incomplete AWD. The results showed that, during dry season, complete AWD is a good water management practice to replace CF as it can help mitigate GHG emissions, save water and increase yield. It was noted that in a case where incomplete AWD happened, although less water was used than the complete AWD but high emissions and yield reduction may occur. Therefore, to avoid incomplete AWD, it is recommended to implement AWD in the area or season with no frequent rainfall. (C) 2019 Elsevier Ltd.

Quynh V D, O Sander.

Applying and scaling up alternate wetting and drying for paddy rice in Vietnam

[R]. International Rice Research Institute and the CGIAR Program on Climate Change, Agriculture and Food Security, 2015

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[J]. Soil Science and Plant Nutrition, 2018, 64 (1): 14-22

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[J]. 农业工程学报, 2022, 38 (S1): 232-239.

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Applicability and abatement potential assessment of alternate wet and dry CH4 mitigation technology in major rice cropping regions in Hunan province of China

[J]. Transactions of the Chinese Society of Agricultural Engineering, 2022, 38 (S1): 232-239 (in Chinese)

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[J]. Field Crops Research, 2017, 203: 173-180

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蔡祖聪, 徐华, 马静. 稻田生态系统CH4和N2O排放[M]. 合肥: 中国科学技术大学出版社, 2009.

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Cai Z C, Xu H, Ma J. CH4 and N2O emissions from paddy ecosystems[M]. Hefei: University of Science and Technology of China Press, 2009 (in Chinese)

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[J]. Global Biogeochemical Cycles, 2005, 19 (2): 1-9

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Yagi K, Sriphirom P, Cha-un N, et al.

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[J]. Soil Science and Plant Nutrition, 2020, 66 (1): 37-49

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Hussain S, Peng S, Fahad S, et al.

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[J]. Environmental Science and Pollution Research, 2015, 22 (5): 3342-3360

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