中国农田施用化学氮肥的固碳潜力及其有效性评价

按照2003年氮肥施用情况和农业专家对不同作物提出的推荐施肥量,设定了“氮肥施用现状”和“按推荐量施肥”两个情景,在搜集和整理全国典型的农业长期定位实验站数据的基础上,将全国划分为4个农业区,分析了两种情景下我国农田土壤的固碳潜力;同时根据我国生产氮肥的化石能源消耗以及施用氮肥的数据,采用国内以及IPCC提供的相关参数,计算了施用化肥导致的温室气体泄漏,并提出“有效固碳潜力”的概念作为评价固碳潜力有效性和固碳措施可行性的标准.我国农田土壤在两种情景下的固碳潜力分别为21.9和30.2 Tg C·a^-1;但两种情景下生产和施用化学氮肥的温室气体泄漏量分别达到了72.9和91.4 Tg C·a^-1,使两种情景下有效固碳潜力分别为-51.0和-61.1 Tg C·a^-1;而“按推荐量施肥”还将增加10.1 Tg C·a^-1的温室气体净排放.因此,施用氮肥在我国农田土壤不具备有效固碳潜力,作为固碳措施不可行.鉴于施用化肥是我国粮食安全的基本保障,建议在保证粮食生产的前提下,提高氮肥利用率,适当减少氮肥施用量,以利于温室气体的减排.     

森林经营与管理下的温室气体排放、碳泄漏和净固碳量研究进展

森林在减缓全球气候变化和大气CO₂浓度升高上具有重要作用.森林经营与管理下的新造林和森林保护具有显著的固碳功能,其中,新造林和森林保护的固碳速率分别为0.04～7.52、0.33～5.20 t C·hm^-2·a^-1.同时,营造林过程中物资的生产和运输导致边界内产生温室气体排放;营造林导致的活动转移、市场效应和生态环境变化导致边界外产生碳泄漏.本文综述了国内外森林经营与管理活动边界内温室气体排放源的界定、计量方法、温室气体排放量与排放速率;边界外碳泄漏的类型、计量方法与碳泄漏量;净固碳量以及温室气体排放和碳泄漏对固碳的抵消强度.边界内温室气体排放对固碳的抵消强度为0.01%～19.3%,进一步考虑碳泄漏时可增至95%.若仅考虑森林经营与管理在边界内直接产生的温室气体排放与可测量的活动转移碳泄漏,森林经营与管理具有较好的净固碳效益,且相比于农田固碳措施在温室气体净减排方面具有更好的应用前景.随着我国各项重大生态工程新一期的开展和对工程固碳效益的关注,为增加重大生态工程对温室气体的净减排量,有必要在工程开展前进行合理规划、在工程开展过程中加强控制和监测以减少工程实施导致的边界内温室气体排放和边界外碳泄漏.     

中国农田土壤生态系统固碳现状和潜力

研究在搜集和整理全国典型农业长期定位实验站数据的基础上,通过自建经验公式估算了不同管理措施下我国农田土壤的固碳能力和潜力.通过施用化肥、秸秆还田、施用有机肥和免耕措施,目前对我国农田土壤碳增加的贡献分别为40.51、23.89、35.83 Tg·a-1和1.17 Tg·a-1,合计为101.4 Tg·a-1,是我国目前能源活动碳总排放量的13.3%.通过情景分析发现,提高化肥施用量、秸秆还田量、有机肥施用量和推广免耕,可以使我国农田土壤的固碳量分别提高到94.91、42.23、41.38 Tg·a-1和3.58 Tg·a-1,合计为182.1Tg·a-1.农田土壤总的固碳潜力相当于目前我国能源活动碳排放量的23.9%,对于全球CO2减排具有重要的作用.     

稻田秸秆还田:土壤固碳与甲烷增排

基于我国农田土壤有机质长期定位试验和稻田甲烷排放试验成果,将全国稻田划分为单季区和双季区.根据土壤有机质试验数据,分析了秸秆还田在我国两个稻田区的单季稻田、水旱轮作稻田和双季稻田的固碳潜力.同时根据我国稻田甲烷排放试验数据,采用取平均排放系数的方法,估算了我国稻田在无秸秆还田情况下的甲烷排放总量;结合IPCC推荐的方法和参数,估算了我国稻田秸秆还田后甲烷排放总量及增排甲烷的全球增温潜势.结果表明:在中国稻田推广秸秆还田的固碳潜力为10.48TgC.a-1,对减缓全球变暖的贡献为38.43TgCO2-eqv.a-1;但秸秆还田后稻田甲烷排放将从无秸秆还田的5.796Tg.a-1增加到9.114Tg.a-1;秸秆还田引起甲烷增排3.318Tg.a-1,其全球增温潜势达82.95TgCO2-eqv.a-1,为土壤固碳减排潜力的2.158倍.可见,推广秸秆还田后,中国稻田增排甲烷的温室效应会大幅抵消土壤固碳的减排效益,是一项重要的温室气体泄漏.     

农田生态系统温室气体减排技术评价指标

目前,国内外学者很少从评价的角度去研究农田温室气体减排技术,缺乏完整性和统一性的评价指标,不利于对农田管理技术进行科学的判断.本研究汇总了当前可作为农田减排技术评价的指标,遵循代表性、客观性、完整性、主导性和可操作性原则,对各项指标的合理性进行了分析,依据我国农业生产实际情况,确定了农田生态系统温室气体减排技术的评价指标.以单位面积粮食产量作为约束性指标,温室气体排放强度(单位产量下的温室气体排放总量)作为综合指标,并将粮食产量、土壤有机碳变化、N2O直接排放、水田CH4排放与农田投入直接和间接排放作为后者的分项指标;依据温室气体排放强度计算公式,能够科学、系统地评价农田减排技术的温室效应,可为我国农田减排技术的提出和推广提供科学依据.     

土地利用对崇明岛围垦区土壤有机碳库和土壤呼吸的影响

土地利用方式是影响农业土壤碳固持和温室气体减排的关键因子之一,而准确地评价土地利用变化的影响往往因土壤本底的不均一和土地利用历史多变而复杂化。为此,在崇明东滩湿地围垦区选取了本底均匀、利用历史简单的几种土地利用类型(水-旱轮作农田、人工林、鱼塘撂荒地),研究其土壤有机碳库和土壤呼吸的变化及其与土壤环境间的关系,以期评价其各自的固碳和温室气体减排潜力。农田土壤的表层(20cm)有机碳和微生物生物量碳含量最高,分别为12.62g/kg和225.34mg/kg,包括苗圃栾树林、水杉林带以及桔园在内的人工林地次之,鱼塘撂荒地最低;但撂荒地深层土壤(40—100cm)的有机碳含量高于其它类型,反映了围垦前湿地土壤有机碳累积的残留影响。土壤呼吸强度的顺序则为鱼塘撂荒地农田桔园苗圃栾树林水杉林带。农耕地在前作小麦收割种植水稻后,土壤CO2通量显著下降,不及旱作时的10%。除农田和撂荒地以外,土壤表层5 cm深处温度可以很好地解释土壤呼吸速率的变化,但在高温高湿季节呼吸速率较为离散。研究表明:在有机质含量较低的土壤中,水-旱轮作可增加土壤有机碳的储量;受人类活动干扰较小的林地土壤,有机碳含量反而有可能低于农田土壤。在中国南方湿润亚热带地区,水旱轮作可较好地协调农业土壤的碳固持和释放过程的矛盾,可能具有相当大的农业减排潜力。     

农田生态系统土壤有机碳库及其影响因子

土壤有机碳(SOC)的数量和质量在很大程度上与维持和提高土壤肥力密切相关。农田生态系统土壤碳库研究一直是农业、生态和环境领域的一个主要方向。土地利用、耕作、作物类型、种植密度、灌溉、施肥以及其他人为活动等,对农田生态系统土壤有机碳库的变化均能产生影响。本文综合评述了农田生态系统土壤有机碳库及其影响因子,土壤碳截获潜力,维持和提高土壤有机碳库的措施,以及农田土壤碳截获在温室气体减排及气候变化中的潜在作用等,最后提出了农田生态系统土壤有机碳库研究的主要方向。     

中国天然林资源保护工程温室气体排放及净固碳能力

基于天然林资源保护工程(简称天保工程)一期(2000—2010年)营造林过程工程边界内碳排放和边界外碳泄漏的计算,分析了天保工程及各区域碳排放和碳泄漏年际变化及影响因素,对比了天保工程及各区域碳排放和碳泄漏的组成特征,研究了天保工程及各区域净固碳量的变化特征。结果表明:天保工程一期西北、中西部地区、南部地区、东北地区和天保工程的碳排放分别为0.89、1.47、0.09、2.45 Tg C;碳泄漏分别为3.17、3.11、6.50、12.78 Tg C。工程措施和碳排放强度的区域性差异导致各区域碳排放组成特征不同。造林及配套森林基础设施建设是西北、中西部地区和南部地区最大的工程措施碳排放;新造林及森林管护是东北地区最大的工程措施碳排放。相应地,各种物资消耗中,建材是西北、中西部地区和南部地区最大的物资碳排放;燃油是东北地区最大的物资碳排放。天保工程在工程边界内外引起的额外温室气体排放量达到15.23 Tg C,抵消了工程固碳效益的9.82%;在西北、中西部地区、南部地区和东北地区的抵消作用分别为10.08%、8.16%和11.24%。天保工程一期净固碳量为139.77 Tg C,年均净固碳量为12.71 Tg C/a。因此,碳排放和碳泄漏对天保工程固碳的抵消较小,工程一期在我国温室气体减排和减缓全球气候变暖上做出了巨大贡献。避免工程基础设施的盲目建设和对工程进行合理规划是减少温室气体排放的可能途径。     

剔除杂草对山核桃林地土壤温室气体排放的影响

森林土壤是CO2、N2O和CH4等温室气体的重要排放源,山核桃是中国特有的高档干果和木本油料树种,林下杂草管理对山核桃林地温室气体排放具有重要影响.采用静态箱-气相色谱法在浙江临安山核桃主产区进行了为期1年的原位试验,研究剔除林下杂草对山核桃林地土壤温室气体排放的影响.结果表明:剔除杂草和留养杂草山核桃林地土壤CO2排放通量呈现一致的季节变化规律:夏秋季高、冬春季低;N2O排放在夏季较高,其他季节变化平稳;CH4的排放无明显季节变化规律.剔除杂草显著降低了土壤CO2排放,促进了N2O排放和CH4吸收.剔除杂草对土壤水溶性有机碳和微生物生物量碳没有显著影响.剔除杂草的山核桃林地土壤排放温室气体的综合增温潜势为15.12 t CO2-e·hm-2·a-1,显著低于留养杂草处理(17.04 t CO2-e·hm-2·a-1).     

土壤有机质对农田管理措施的动态响应

土壤有机质在农田肥力、环境保护、农业可持续发展等方面具有重要意义。它不仅决定农作物产量,而且在全球碳素循环中起着重要作用。由于大气CO2浓度升高与全球气候变暖等一系列环境问题的加剧,全球碳素循环受到越来越多的关注。农田具有大气CO2源和库的双重潜力。历史上由于人类对农田的过度开垦和耕种,造成土壤有机质含量大幅度下降,降低了农田的作物产量潜力;同时导致大量的碳以CO2形式由陆地生态系统排放到大气圈,加剧了全球温室效应。大量研究结果表明,诸如耕作、种植制度、施肥等农田管理措施能够显著地影响土壤有机质动态,而免耕、提高复种指数、合理的轮作换茬、有机肥料和化肥的施用以及弃耕农田还林还草等保护性管理措施则能够提高农田土壤有机质含量,使农田起到大气CO2汇的作用。综述了近年来农田管理对土壤有机质动态影响研究方面的进展。     

Mitigating the greenhouse gas balance of ruminant production systems through carbon sequestration in grasslands

Soil carbon sequestration (enhanced sinks) is the mechanism responsible for most of the greenhouse gas (GHG) mitigation potential in the agriculture sector. Carbon sequestration in grasslands can be determined directly by measuring changes in soil organic carbon (SOC) stocks and indirectly by measuring the net balance of C fluxes. A literature search shows that grassland C sequestration reaches on average 5 ± 30 g C/m2 per year according to inventories of SOC stocks and -231 and 77 g C/m2 per year for drained organic and mineral soils, respectively, according to C flux balance. Off-site C sequestration occurs whenever more manure C is produced by than returned to a grassland plot. The sum of on- and off-site C sequestration reaches 129, 98 and 71 g C/m2 per year for grazed, cut and mixed European grasslands on mineral soils, respectively, however with high uncertainty. A range of management practices reduce C losses and increase C sequestration: (i) avoiding soil tillage and the conversion of grasslands to arable use, (ii) moderately intensifying nutrient-poor permanent grasslands, (iii) using light grazing instead of heavy grazing, (iv) increasing the duration of grass leys; (v) converting grass leys to grass-legume mixtures or to permanent grasslands. With nine European sites, direct emissions of N2O from soil and of CH4 from enteric fermentation at grazing, expressed in CO2 equivalents, compensated 10% and 34% of the on-site grassland C sequestration, respectively. Digestion inside the barn of the harvested herbage leads to further emissions of CH4 and N2O by the production systems, which were estimated at 130 g CO2 equivalents/m2 per year. The net balance of on- and off-site C sequestration, CH4 and N2O emissions reached 38 g CO2 equivalents/m2 per year, indicating a non-significant net sink activity. This net balance was, however, negative for intensively managed cut sites indicating a source to the atmosphere. In conclusion, this review confirms that grassland C sequestration has a strong potential to partly mitigate the GHG balance of ruminant production systems. However, as soil C sequestration is both reversible and vulnerable to disturbance, biodiversity loss and climate change, CH4 and N2O emissions from the livestock sector need to be reduced and current SOC stocks preserved.     

The potential to mitigate global warming with no-tillage management is only realized when practised in the long term

No‐tillage (NT) management has been promoted as a practice capable of offsetting greenhouse gas (GHG) emissions because of its ability to sequester carbon in soils. However, true mitigation is only possible if the overall impact of NT adoption reduces the net global warming potential (GWP) determined by fluxes of the three major biogenic GHGs (i.e. CO₂, N₂O, and CH₄). We compiled all available data of soil‐derived GHG emission comparisons between conventional tilled (CT) and NT systems for humid and dry temperate climates. Newly converted NT systems increase GWP relative to CT practices, in both humid and dry climate regimes, and longer‐term adoption (>10 years) only significantly reduces GWP in humid climates. Mean cumulative GWP over a 20‐year period is also reduced under continuous NT in dry areas, but with a high degree of uncertainty. Emissions of N₂O drive much of the trend in net GWP, suggesting improved nitrogen management is essential to realize the full benefit from carbon storage in the soil for purposes of global warming mitigation. Our results indicate a strong time dependency in the GHG mitigation potential of NT agriculture, demonstrating that GHG mitigation by adoption of NT is much more variable and complex than previously considered, and policy plans to reduce global warming through this land management practice need further scrutiny to ensure success.     

Greenhouse gas mitigation in agriculture

Agricultural lands occupy 37% of the earth's land surface. Agriculture accounts for 52 and 84% of global anthropogenic methane and nitrous oxide emissions. Agricultural soils may also act as a sink or source for CO2, but the net flux is small. Many agricultural practices can potentially mitigate greenhouse gas (GHG) emissions, the most prominent of which are improved cropland and grazing land management and restoration of degraded lands and cultivated organic soils. Lower, but still significant mitigation potential is provided by water and rice management, set-aside, land use change and agroforestry, livestock management and manure management. The global technical mitigation potential from agriculture (excluding fossil fuel offsets from biomass) by 2030, considering all gases, is estimated to be approximately 5500-6000Mt CO2-eq.yr-1, with economic potentials of approximately 1500-1600, 2500-2700 and 4000-4300Mt CO2-eq.yr-1 at carbon prices of up to 20, up to 50 and up to 100 US$ t CO2-eq.-1, respectively. In addition, GHG emissions could be reduced by substitution of fossil fuels for energy production by agricultural feedstocks (e.g. crop residues, dung and dedicated energy crops). The economic mitigation potential of biomass energy from agriculture is estimated to be 640, 2240 and 16 000Mt CO2-eq.yr-1 at 0-20, 0-50 and 0-100 US$ t CO2-eq.-1, respectively.     

A Miscanthus plantation can be carbon neutral without increasing soil carbon stocks

National governments and international organizations perceive bioenergy, from crops such as Miscanthus, to have an important role in mitigating greenhouse gas (GHG) emissions and combating climate change. In this research, we address three objectives aimed at reducing uncertainty regarding the climate change mitigation potential of commercial Miscanthus plantations in the United Kingdom: (i) to examine soil temperature and moisture as potential drivers of soil GHG emissions through four years of parallel measurements, (ii) to quantify carbon (C) dynamics associated with soil sequestration using regular measurements of topsoil (0–30 cm) C and the surface litter layer and (iii) to calculate a life cycle GHG budget using site‐specific measurements, enabling the GHG intensity of Miscanthus used for electricity generation to be compared against coal and natural gas. Our results show that methane (CH₄) and nitrous oxide (N₂O) emissions contributed little to the overall GHG budget of Miscanthus, while soil respiration offset 30% of the crop's net aboveground C uptake. Temperature sensitivity of soil respiration was highest during crop growth and lowest during winter months. We observed no significant change in topsoil C or nitrogen stocks following 7 years of Miscanthus cultivation. The depth of litter did, however, increase significantly, stabilizing at approximately 7 tonnes dry biomass per hectare after 6 years. The cradle‐to‐farm gate GHG budget of this crop indicated a net removal of 24.5 t CO₂‐eq ha^?1 yr^?1 from the atmosphere despite no detectable C sequestration in soils. When scaled up to consider the full life cycle, Miscanthus fared very well in comparison with coal and natural gas, suggesting considerable CO₂ offsetting per kWh generated. Although the comparison does not account for the land area requirements of the energy generated, Miscanthus used for electricity generation can make a significant contribution to climate change mitigation even when combusted in conventional steam turbine power plants.     

Plant roots and GHG mitigation in native perennial bioenergy cropping systems

Native perennial bioenergy crops can mitigate greenhouse gases (GHG) by displacing fossil fuels with renewable energy and sequestering atmospheric carbon (C) in soil and roots. The relative contribution of root C to net GHG mitigation potential has not been compared in perennial bioenergy crops ranging in species diversity and N fertility. We measured root biomass, C, nitrogen (N), and soil organic carbon (SOC) in the upper 90 cm of soil for five native perennial bioenergy crops managed with and without N fertilizer. Bioenergy crops ranged in species composition and were annually harvested for 6 (one location) and 7 years (three locations) following the seeding year. Total root biomass was 84% greater in switchgrass (Panicum virgatum L.) and a four‐species grass polyculture compared to high‐diversity polycultures; the difference was driven by more biomass at shallow soil depth (0–30 cm). Total root C (0–90 cm) ranged from 3.7 Mg C ha^?1 for a 12‐species mixture to 7.6 Mg C ha^?1 for switchgrass. On average, standing root C accounted for 41% of net GHG mitigation potential. After accounting for farm and ethanol production emissions, net GHG mitigation potential from fossil fuel offsets and root C was greatest for switchgrass (?8.4 Mg CO2e ha^?1 yr^?1) and lowest for high‐diversity mixtures (?4.5 Mg CO2e ha^?1 yr^?1). Nitrogen fertilizer did not affect net GHG mitigation potential or the contribution of roots to GHG mitigation for any bioenergy crop. SOC did not change and therefore did not contribute to GHG mitigation potential. However, associations among SOC, root biomass, and root C : N ratio suggest greater long‐term C storage in diverse polycultures vs. switchgrass. Carbon pools in roots have a greater effect on net GHG mitigation than SOC in the short‐term, yet variation in root characteristics may alter patterns in long‐term C storage among bioenergy crops.     

Effects of biochar application on soil greenhouse gas fluxes: a meta‐analysis

Biochar application to soils may increase carbon (C) sequestration due to the inputs of recalcitrant organic C. However, the effects of biochar application on the soil greenhouse gas (GHG) fluxes appear variable among many case studies; therefore, the efficacy of biochar as a carbon sequestration agent for climate change mitigation remains uncertain. We performed a meta‐analysis of 91 published papers with 552 paired comparisons to obtain a central tendency of three main GHG fluxes (i.e., CO₂, CH₄, and N₂O) in response to biochar application. Our results showed that biochar application significantly increased soil CO₂ fluxes by 22.14%, but decreased N₂O fluxes by 30.92% and did not affect CH₄ fluxes. As a consequence, biochar application may significantly contribute to an increased global warming potential (GWP) of total soil GHG fluxes due to the large stimulation of CO₂ fluxes. However, soil CO₂ fluxes were suppressed when biochar was added to fertilized soils, indicating that biochar application is unlikely to stimulate CO₂ fluxes in the agriculture sector, in which N fertilizer inputs are common. Responses of soil GHG fluxes mainly varied with biochar feedstock source and soil texture and the pyrolysis temperature of biochar. Soil and biochar pH, biochar applied rate, and latitude also influence soil GHG fluxes, but to a more limited extent. Our findings provide a scientific basis for developing more rational strategies toward widespread adoption of biochar as a soil amendment for climate change mitigation.     

Modelling the impact of agricultural management on soil carbon stocks at the regional scale: the role of lateral fluxes

Agricultural management has received increased attention over the last decades due to its central role in carbon (C) sequestration and greenhouse gas mitigation. Yet, regardless of the large body of literature on the effects of soil erosion by tillage and water on soil organic carbon (SOC) stocks in agricultural landscapes, the significance of soil redistribution for the overall C budget and the C sequestration potential of land management options remains poorly quantified. In this study, we explore the role of lateral SOC fluxes in regional scale modelling of SOC stocks under three different agricultural management practices in central Belgium: conventional tillage (CT), reduced tillage (RT) and reduced tillage with additional carbon input (RT+i). We assessed each management scenario twice: using a conventional approach that did not account for lateral fluxes and an alternative approach that included soil erosion‐induced lateral SOC fluxes. The results show that accounting for lateral fluxes increased C sequestration rates by 2.7, 2.5 and 1.5 g C m^?2 yr^?1 for CT, RT and RT+i, respectively, relative to the conventional approach. Soil redistribution also led to a reduction of SOC concentration in the plough layer and increased the spatial variability of SOC stocks, suggesting that C sequestration studies relying on changes in the plough layer may underestimate the soil's C sequestration potential due to the effects of soil erosion. Additionally, lateral C export from cropland was in the same of order of magnitude as C sequestration; hence, the fate of C exported from cropland into other land uses is crucial to determine the ultimate impact of management and erosion on the landscape C balance. Consequently, soil management strategies targeting C sequestration will be most effective when accompanied by measures that reduce soil erosion given that erosion loss can balance potential C uptake, particularly in sloping areas.     

Importance of mangrove plantations for climate change mitigation in Bangladesh

Mangroves have been identified as blue carbon ecosystems that are natural carbon sinks. In Bangladesh, the establishment of mangrove plantations for coastal protection has occurred since the 1960s, but the plantations may also be a sustainable pathway to enhance carbon sequestration, which can help Bangladesh meet its greenhouse gas (GHG) emission reduction targets, contributing to climate change mitigation. As a part of its Nationally Determined Contribution (NDC) under the Paris Agreement 2016, Bangladesh is committed to limiting the GHG emissions through the expansion of mangrove plantations, but the level of carbon removal that could be achieved through the establishment of plantations has not yet been estimated. The mean ecosystem carbon stock of 5–42 years aged (average age: 25.5 years) mangrove plantations was 190.1 (±30.3) Mg C ha⁻¹, with ecosystem carbon stocks varying regionally. The biomass carbon stock was 60.3 (±5.6) Mg C ha⁻¹ and the soil carbon stock was 129.8 (±24.8) Mg C ha⁻¹ in the top 1 m of which 43.9 Mg C ha⁻¹ was added to the soil after plantation establishment. Plantations at age 5 to 42 years achieved 52% of the mean ecosystem carbon stock calculated for the reference site (Sundarbans natural mangroves). Since 1966, the 28,000 ha of established plantations to the east of the Sundarbans have accumulated approximately 76,607 Mg C year⁻¹ sequestration in biomass and 37,542 Mg C year⁻¹ sequestration in soils, totaling 114,149 Mg C year⁻¹. Continuation of the current plantation success rate would sequester an additional 664,850 Mg C by 2030, which is 4.4% of Bangladesh's 2030 GHG reduction target from all sectors described in its NDC, however, plantations for climate change mitigation would be most effective 20 years after establishment. Higher levels of investment in mangrove plantations and higher plantation establishment success could contribute up to 2,098,093 Mg C to blue carbon sequestration and climate change mitigation in Bangladesh by 2030.     

Cropland intensification mediates the radiative balance of greenhouse gas emissions and soil carbon sequestration in maize systems of sub-Saharan Africa

Sub-Saharan Africa (SSA) must undertake proper cropland intensification for higher crop yields while minimizing climate impacts. Unfortunately, no studies have simultaneously quantified greenhouse gas (GHG; CO₂, CH₄, and N₂O) emissions and soil organic carbon (SOC) change in SSA croplands, leaving it a blind spot in the accounting of global warming potential (GWP). Here, based on 2-year field monitoring of soil emissions of CO₂, CH₄, and N₂O, as well as SOC changes in two contrasting soil types (sandy vs. clayey), we provided the first, full accounting of GWP for maize systems in response to cropland intensifications (increasing nitrogen rates and in combination with crop residue return) in SSA. To corroborate our field observations on SOC change (i.e., 2-year, a short duration), we implemented a process-oriented model parameterized with field data to simulate SOC dynamic over time. We further tested the generality of our findings by including a literature synthesis of SOC change across maize-based systems in SSA. We found that nitrogen application reduced SOC loss, likely through increased biomass yield and consequently belowground carbon allocation. Residue return switched the direction of SOC change from loss to gain; such a benefit (SOC sequestration) was not compromised by CH₄ emissions (negligible) nor outweighed by the amplified N₂O emissions, and contributed to negative net GWP. Overall, we show encouraging results that, combining residue and fertilizer-nitrogen input allowed for sequestering 82–284 kg of CO₂-eq per Mg of maize grain produced across two soils. All analyses pointed to an advantage of sandy over clayey soils in achieving higher SOC sequestration targets, and thus call for a re-evaluation on the potential of sandy soils in SOC sequestration across SSA croplands. Our findings carry important implications for developing viable intensification practices for SSA croplands in mitigating climate change while securing food production.