Sustainable Approaches to Agricultural Greenhouse Gas Mitigation in the EU: Practices, Mechanisms, and Policy Integration

Abstract

The agricultural sector has a significant impact on the global carbon cycle, contributing substantially to greenhouse gas (GHG) emissions through various practices and processes. This review paper examines the significant role of the agricultural sector in the global carbon cycle, highlighting its substantial contribution to GHG emissions through diverse practices and processes. The study explores the trends and spatial distribution of agricultural GHG emissions at both the global level and within the European Union (EU). Emphasis is placed on the principal gases released by this sector—methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂)—with detailed attention to their sources, levels, environmental impacts, and key strategies to mitigate and control their effects, based on the latest scientific data. The paper further investigates emissions originating from livestock production, along with mitigation approaches including feed additives, selective breeding, and improved manure management techniques. Soil-derived emissions, particularly N₂O and CO₂ resulting from fertilizer application and microbial activity, are thoroughly explored. Additionally, the influence of various agricultural practices such as tillage, crop rotation, and fertilization on emission levels is analyzed, supported by updated data from recent literature. Special focus is given to the underlying mechanisms that regulate these emissions and the effectiveness of management interventions in reducing their magnitude. The research also evaluates current European legislative measures aimed at lowering agricultural emissions and promoting climate-resilient, sustainable farming systems. Various mitigation strategies—ranging from optimized land and nutrient management to the application of nitrification inhibitors and soil amendments are assessed for both their practical feasibility and long-term impact.

1. Introduction

Human activities, including modern agriculture, contribute significantly to the production of greenhouse gases (GHGs), which have been increasing since the beginning of the industrial era. Some greenhouse gases, such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆), are emitted exclusively by human activities.

Agriculture is a major source of greenhouse gases, primarily carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). Each gas has a different global warming potential and atmospheric lifetime, contributing to climate change to varying degrees due to its distinct impacts and persistence in the atmosphere [1].

Beyond the overall contribution of agriculture, soils play a particularly important role, accounting for about 15% of anthropogenic climate warming, mainly through CO₂ (74%), N₂O (17%), and CH₄ (9%) emissions [2]. In agricultural systems, CH₄ originates largely from enteric fermentation in ruminants and manure management [3], while N₂O emissions result from soil microbial processes such as nitrification and denitrification, driven by nitrogen inputs from fertilizers and manure [4].

Overall, agrifood systems contribute approximately one-third of global GHG emissions [5], with agriculture alone responsible for about 49% of CH₄ and 63% of N₂O emissions within the European Union.

Beyond direct emissions, agriculture indirectly elevates GHG levels through land-use changes, most notably deforestation, releasing carbon stored in soils and vegetation [6].

Emission mitigation strategies in agriculture are based on a variety of strategies targeting both crop production and livestock systems, as follows: changes in agronomic practices [4,7], modifying animal diets [8,9], manure treatment [10], and biological innovations [11]. While numerous mitigation options have been identified, their implementation is influenced by the heterogeneity of farming systems and socio-economic conditions. Differences in farm structure, diversity of crops, resource availability, and policy support shape the feasibility and effectiveness of mitigation practices [12,13]. Moreover, trade-offs often exist between emission reduction, food security, and farmers’ livelihoods, highlighting the need for context-specific and balanced approaches to sustainable agricultural management.

However, agriculture is not solely a source of GHG emissions; it can also serve as a carbon sink by storing carbon in soils and plant biomass through a process known as carbon sequestration. Soil carbon sequestration is a natural and effective way to lower atmospheric CO₂ levels, playing an important role in mitigating climate change. It works by capturing CO₂ from the atmosphere and storing it in the soil as organic carbon [14]. This not only reduces greenhouse gas concentrations but also improves soil health and fertility [15]. Agricultural practices such as reduced tillage, cover cropping, and improved soil management can help reduce emissions while increasing the soil’s capacity to store carbon [16].

This review analyzes GHG emissions (CO₂, CH₄, N₂O) by examining their sources, mechanisms, and management practices at the global and regional levels. It highlights how agricultural activities such as fertilization, soil and residue management, and livestock production contribute to climate change. By linking emission sources with mitigation strategies and relevant policy frameworks, this review synthesizes current scientific knowledge and management approaches, offering an integrative reference for advancing sustainable agricultural practices.

The novelty of this work lies in its integrated approach, combining scientific evidence on emission sources with mitigation measures and policy analysis, offering a comprehensive perspective on sustainable agricultural development within the EU context.

This paper is structured into nine sections, which explore the temporal evolution of CO₂, CH₄, and N₂O emissions at both the European Union and global levels, identify the primary agricultural sources of these emissions, and discuss current strategies for their mitigation and control. For a better understanding of the overall content, the chapters and subchapters are illustrated in Figure 1.

2. Methodology

A literature search was conducted across commonly accessed scientific databases, including Web of Science, Scopus, PubMed, and Google Scholar, as well as in reports from international organizations such as FAO and EEA. The search focused on the role of the agricultural sector in GHG emissions and mitigation strategies. Various keywords and their combinations were used to ensure a comprehensive search that captured relevant papers across different agricultural practices, GHG types, and mitigation strategies. Few examples of used keywords include: “greenhouse gas emissions”, “livestock”, “manure management”, “agriculture AND greenhouse gas emissions”, “mitigation strategies AND agriculture”, “methane emissions AND agriculture”, “carbon dioxide emissions AND agriculture”, “nitrous oxide AND agriculture”.

Articles were included in the evaluation if they were published in peer-reviewed journals between 2000 and 2025, focused on GHG emissions from agriculture or livestock, addressed mitigation strategies or sustainable farming practices, and were available in English. Additionally, among the selected papers, some were used for backward and forward snowballing techniques to identify additional relevant studies, which were then included in our database for comprehensive data collection.

Articles were excluded if they did not provide data on GHG emissions, focused exclusively on forestry or non-agricultural sectors, or were published in journals with no impact factor. These criteria ensured that the selected literature was relevant and provided recent data on the subject.

Selected studies included research articles, review papers, and reports containing experimental data.

3. Overview of GHG Emissions in Agriculture

Agriculture contributes approximately 18% of total GHG emissions through activities involving soils, fertilizers, livestock, and residues [17]. Carbon dioxide, mainly produced from fossil fuel use and land-use changes, accounts for only 7% of agricultural emissions. Methane, primarily emitted from enteric fermentation in ruminants and manure management, is the largest contributor at nearly 50% of agricultural emissions. Nitrous oxide, released from agricultural soils and from manure application, accounts for about 30% of emissions and has a particularly strong impact on global warming due to its high Global Warming Potential (GWP), ranging from 265 to 310 [18,19].

Figure 2 illustrates the main sources of GHG emissions in agriculture and their links to specific agricultural activities and practices.

In 2022, global agrifood systems released 16.2 billion tons of CO₂ equivalent (Gt CO₂e), a figure that remained almost unchanged from 2021 and represented a 10% increase compared to 2000 [20]. Fertilizer production and application (including manure and synthetic types) generate 2.6 Gt CO₂e per year [21].

Agricultural emissions vary regionally due to differences in farming practices, livestock density, and land-use patterns. These variations influence the types and magnitudes of emissions, with regions dominated by ruminant livestock showing higher CH₄ emissions [22], while areas with intensive cropping tend to have greater emissions from fertilizer use [23]. More than 60% of N₂O emissions are attributed to agriculture, largely due to the use of organic and inorganic fertilizers [23].

Moreover, in addition to its contributions to greenhouse gas emissions, agriculture can also serve as a potential carbon sink, removing carbon dioxide from the atmosphere through processes such as soil carbon sequestration and biomass accumulation. Maintaining and increasing soil organic carbon through practices like cover cropping, reduced tillage, agroforestry, and the addition of organic amendments can enhance this sink function while simultaneously improving soil health and fertility [24].

3.1. GHG Emissions from Agriculture in the EU and Worldwide

Between 1970 and 2023, agricultural GHG emissions showed contrasting trends in the European Union and globally (Figure 3, Figure 4 and Figure 5).

In the EU, CO₂ emissions from agriculture peaked between 1983 and 1986 at 18.65 Mt CO₂e, then steadily declined to 9.64 Mt CO₂e by 2023, nearly halving compared to 1990 levels (Figure 3) [25]. This reduction reflects the impact of regulatory measures and agricultural policy reforms. Globally, agricultural CO₂ emissions rose significantly, accelerating around 1976 and almost doubling by 1988 to 96.23 Mt CO₂e. Emissions continued to increase, surpassing 140 Mt CO₂e by 2019, reaching 143.62 Mt CO₂e in 2023, almost three times the 1970 level.

EU CH₄ emissions peaked in 1984 at 343.10 Mt CO₂e and then declined by 30.55% to 238.25 Mt CO₂e in 2023 (Figure 4) [26]. This reduction began in the 1990s due to policy efforts, improved waste management, and structural shifts in agriculture and energy sectors. After 2010, emissions stabilized but maintained a downward trend. Globally, CH₄ emissions increased by 28.54% from 1970 to 2023, continuing a generally rising trend even during the COVID-19 pandemic, when EU emissions were declining. In 2023, the EU accounted for 5.16% of global CH₄ emissions.

N₂O emissions in the EU rose until peaking at 184.85 Mt CO₂e in 1988, then steadily decreased by 28.23% to 132.66 Mt CO₂e by 2023 (Figure 5) [27]. This decline reflects environmental regulation and sustainable agricultural practices. Although there were fluctuations during the 2000s and 2010s, the overall downward trend persisted. Conversely, global N₂O emissions nearly doubled during the same period, continuing to increase even amid the COVID-19 pandemic.

Overall, the EU has successfully reduced agricultural emissions of CO₂, CH₄, and N₂O through comprehensive legislative frameworks, policy reforms, and the adoption of sustainable agricultural practices. This contrasts with the global trend of rising emissions, largely driven by expanding agricultural activities and weaker regulatory enforcement, highlighting the urgent need for international cooperation, especially in rapidly developing regions and areas with intensive agriculture.

The variation in the reduction in emissions in the EU compared to global trends can be explained by several factors, including regulatory and policy measures (further details are presented in Section 4), technological and management improvements such as crop rotation and cover cropping, and strong economic and political commitment [28]. In addition, global trends continue to show an increase in emissions, driven by expanding agricultural activities and less stringent regulations in developing countries, mainly [29].

3.2. Agricultural GHG Emissions in the EU by Source

According to data provided by the European Environment Agency [19] (Figure 6), CH₄ emissions from enteric fermentation have shown a gradual decline since 2005, decreasing from 188.83 Mt CO₂e to 176.76 Mt CO₂e in 2023. The decrease in CH₄ emissions from enteric fermentation likely reflects improvements in livestock management, such as better feeding strategies, dietary adjustments, or breeding programs aimed at reducing CH₄ production during digestion [30,31].

Similarly, N₂O emissions from agricultural soils declined overall from 115.86 Mt CO₂e in 2005 to 106.61 Mt CO₂e in 2023. However, within this period, emissions showed a pattern of fluctuations with both increases and decreases. The episodes of rising N₂O emissions can be attributed to factors such as increased nitrogen fertilizer application, shifts in agricultural practices, and intensified farming systems [32].

Further details regarding N₂O emissions from soil are discussed in Section 7. However, the reduction in recent years suggests that farmers may have adopted more precision agriculture techniques to manage fertilizer application more effectively, leading to reduced N₂O emissions [18].

Another possible factor is the promotion of sustainable agricultural practices [33], such as improved soil management or the use of slow-release or controlled-release fertilizers, nitrification inhibitors, as discussed in Section 7.2.

Emissions from manure management declined from 68.48 Mt CO₂e to 60.78 Mt CO₂e over the same period. This downward trend likely reflects improvements in manure-handling techniques, including better manure storage systems that reduce GHG emissions, as well as optimized land application practices [34]. Additional information regarding this issue is provided in Section 6.2.2.

In contrast, emissions from other agricultural sources remained relatively stable, increasing only slightly from 13.65 Mt CO₂e in 2005 to 14.13 Mt CO₂e in 2023. This stability suggests limited changes in land management and crop residue burning practices [17].

Concluding, significant, though insufficient, reductions in agricultural GHG emissions, particularly from enteric fermentation and manure management, have been achieved through improved livestock and manure practices. However, variability in soil N₂O emissions persists due to ongoing challenges in fertilizer use and soil management. To meet the EU’s 2050 climate-neutrality goals [35], continued monitoring, coupled with broader adoption of precision agriculture and sustainable soil management techniques, is essential to ensure sustained progress in GHG emission mitigation.

4. EU Legislation Regulating GHG Emissions from Agriculture

In response to the need for controlling GHG emissions to more effectively manage climate change and mitigate its impacts, the European Union has developed a series of legislative and policy frameworks addressing GHG emissions across various sectors, including agriculture (Figure 7).

These frameworks are designed to reduce emissions, promote sustainability, and align with the EU’s broader climate goals, such as achieving climate neutrality by 2050 and reducing emissions by at least 55% by 2030 compared to 1990 levels.

Based on the knowledge provided by the documentation in this paper, the EU’s climate objectives mentioned above are difficult to fulfill but are still achievable. There is progress that was observed during the time that suggests that ongoing policy frameworks and technological advances are effective. The objectives will be achieved through further innovation, widespread adoption of best practices, and compliance with all current regulations, as well as those that will complement the existing ones.

The development of these policies highlights the increasing focus on sustainable farming practices and carbon sequestration in agriculture, a sector considered central to the EU’s climate strategy.

The European Union has implemented several policies and frameworks to guide the sector toward more sustainable practices (Table 1). Key among these is the Common Agricultural Policy (CAP), which has been consistently updated to encourage sustainable agricultural methods and contribute to the EU’s climate objectives. Additionally, regulations like the Land Use, Land-Use Change, and Forestry (LULUCF) Regulation support practices that enhance carbon sequestration in soils and reduce emissions from land management. Policies such as the “Farm to Fork” strategy and the European Green Deal further integrate agriculture into the broader transition to a green and low-emission economy. These efforts collectively create a comprehensive policy framework that is essential for achieving the EU’s emission-reduction targets and promoting sustainability in the agricultural sector.

The EU Emissions Trading System (EU ETS) is a cap-and-trade scheme that applies to sectors like power generation and heavy industry, setting a limit on emissions and allowing trading of allowances to reduce emissions cost-effectively [36]. Agricultural GHG emissions, which are not covered by the EU ETS, are managed under the Effort Sharing Regulation (ESR). The ESR sets binding national reduction targets for sectors like agriculture, transport, and buildings, ensuring that non-ETS emissions, such as CH₄ and N₂O from farming, contribute to the EU’s overall climate goals [37]. Under the ESR, each Member State receives an annual emission allocation (AEA) for non-ETS sectors, including agriculture. States must implement measures like improving manure management, optimizing feed, and promoting sustainable farming practices. Flexibility mechanisms, such as banking, borrowing, and trading AEAs, allow for greater flexibility in meeting emission targets [37].

Table 1. EU legislation and policy frameworks for reducing agricultural GHG emissions.

Legislation/Policy Frameworks	Description	Refs.
Effort Sharing Decision (ESD) (adopted in 2009)	Member States were required: – to cap their GHG emissions in the Effort Sharing sectors annually from 2013 to 2020; – to achieve a collective reduction of approximately 10% in total EU emissions from the sectors covered by 2020, compared to 2005 levels. By 2020, the EU emissions within the scope of the Effort Sharing Decision were 16.3% lower than in 2005 (overachievement of the initial target). Agricultural emissions decreased by 3% compared to 2005.	[38]
Effort Sharing Regulation (ESR) (adopted in 2018, amended in 2023)	– Sets national targets for each EU Member State to reduce GHG emissions by 2030 in key sectors, including agriculture. – In 2023, the target was to reduce emissions by 30% compared to 2025 levels. – The amended form introduces new targets, with Member States collectively contributing to a 40% emissions reduction in the Effort Sharing sectors compared to 2005 levels. – The regulation also aims for a 55% reduction in total EU emissions by 2030 (compared to 1990 levels) and the achievement of climate neutrality by 2050.	[39]
Land Use, Land-Use Change and Forestry (LULUCF) Regulation (adopted in 2018, amended in 2023)	– Supports farming practices that store carbon and reduce land-use related CO2 emissions. – The LULUCF Regulation outlines how the EU tracks and manages GHG emissions and carbon removals associated with land-use and forestry.	[40]
European Green Deal (EGD) (adopted in 2019)	The European Commission has introduced a series of proposals to align the EU’s climate, energy, transport, and taxation policies with the goal of reducing net GHG emissions by at least 55% by 2030 compared to 1990 levels.	[41]
Farm to Fork Strategy (initiated in 2020)	It is a policy framework within the EGD aimed at creating a sustainable food system. It consists of actions designed to reduce GHG emissions by increasing organic farming and promoting sustainable agricultural practices (such as lower input usage).	[42]
EU Climate Law (ECL) (adopted in 2021)	The law also establishes an intermediate target of reducing net GHG emissions by at least 55% by 2030, compared to 1990 levels, and promotes sustainable land-use, emission-reduction strategies in agriculture.	[43]
Common Agricultural Policy (CAP) (launched in 1962; in 2021, the agreement on the reform of the CAP was formally adopted)	The CAP offers both legislative and financial instruments that encourage sustainable farming methods aimed at cutting GHG emissions, conserving natural resources, and thereby helping to implement the EU’s climate goals within the agricultural sector.	[44]

Table 1. EU legislation and policy frameworks for reducing agricultural GHG emissions.

Legislation/Policy Frameworks	Description	Refs.
Effort Sharing Decision (ESD) (adopted in 2009)	Member States were required: – to cap their GHG emissions in the Effort Sharing sectors annually from 2013 to 2020; – to achieve a collective reduction of approximately 10% in total EU emissions from the sectors covered by 2020, compared to 2005 levels. By 2020, the EU emissions within the scope of the Effort Sharing Decision were 16.3% lower than in 2005 (overachievement of the initial target). Agricultural emissions decreased by 3% compared to 2005.	[38]
Effort Sharing Regulation (ESR) (adopted in 2018, amended in 2023)	– Sets national targets for each EU Member State to reduce GHG emissions by 2030 in key sectors, including agriculture. – In 2023, the target was to reduce emissions by 30% compared to 2025 levels. – The amended form introduces new targets, with Member States collectively contributing to a 40% emissions reduction in the Effort Sharing sectors compared to 2005 levels. – The regulation also aims for a 55% reduction in total EU emissions by 2030 (compared to 1990 levels) and the achievement of climate neutrality by 2050.	[39]
Land Use, Land-Use Change and Forestry (LULUCF) Regulation (adopted in 2018, amended in 2023)	– Supports farming practices that store carbon and reduce land-use related CO2 emissions. – The LULUCF Regulation outlines how the EU tracks and manages GHG emissions and carbon removals associated with land-use and forestry.	[40]
European Green Deal (EGD) (adopted in 2019)	The European Commission has introduced a series of proposals to align the EU’s climate, energy, transport, and taxation policies with the goal of reducing net GHG emissions by at least 55% by 2030 compared to 1990 levels.	[41]
Farm to Fork Strategy (initiated in 2020)	It is a policy framework within the EGD aimed at creating a sustainable food system. It consists of actions designed to reduce GHG emissions by increasing organic farming and promoting sustainable agricultural practices (such as lower input usage).	[42]
EU Climate Law (ECL) (adopted in 2021)	The law also establishes an intermediate target of reducing net GHG emissions by at least 55% by 2030, compared to 1990 levels, and promotes sustainable land-use, emission-reduction strategies in agriculture.	[43]
Common Agricultural Policy (CAP) (launched in 1962; in 2021, the agreement on the reform of the CAP was formally adopted)	The CAP offers both legislative and financial instruments that encourage sustainable farming methods aimed at cutting GHG emissions, conserving natural resources, and thereby helping to implement the EU’s climate goals within the agricultural sector.	[44]

Considering national targets under the Effort Sharing Regulation (ESR), GHG emissions varied significantly among EU Member States between 2005 and 2022. For example, Estonia, Latvia, and Bulgaria recorded substantial increases of 31.46%, 25.85%, and 19.72%, respectively (Figure 8) [19]. In contrast, Croatia and Slovakia achieved the largest reductions, with decreases of 26.59% and 23.68%. Under current measures, projections indicate further increases in emissions for some countries, such as Estonia and Bulgaria, while others, including Croatia and Denmark, are expected to see significant reductions.

Additionally, countries like Ireland, Austria, and Luxembourg, which currently show increasing trends, are projected to reverse these patterns and achieve notable emission reductions by 2030 if additional mitigation measures are implemented. These measures may include enhanced manure management techniques (such as anaerobic digestion, improved storage), adoption of precision agriculture to optimize fertilizer use, reduction in livestock numbers where feasible, and implementation of agroforestry or carbon sequestration practices.

When comparing the evolution of emissions among countries, Estonia and Bulgaria show the highest projected increases in GHG emissions by 2030 under both current and additional measures. In contrast, Croatia is projected to achieve the greatest overall reduction, with emissions expected to fall by more than 26% by 2030.

At the EU-27 level, emissions decreased by 5.45% between 2005 and 2022. With the implementation of additional measures, projections indicate a further reduction of 7.37% by 2030 [19].

Although the reductions in agricultural GHG emissions achieved by the EU need to be maintained, or even further decreased through the implementation of additional measures, it is important to highlight that these legislative regulations have been effective so far. This is especially evident when analyzing the trend of GHG emissions globally over time (Figure 3, Figure 4 and Figure 5) [25,26,27,45]. This demonstrates the critical role of legislation in driving emissions reductions in one of the most challenging sectors for climate policy.

5. Carbon Dioxide Emissions from Agricultural Practices

Agricultural systems contribute significantly to CO₂ emissions through both natural processes and human activities. Major sources include deforestation and land-use change, which release large amounts of carbon stored in vegetation and soils [46].

Additional emissions arise from burning crop residues [47], fossil fuel use in machinery [48], and soil tillage [49], which accelerates the breakdown of organic matter (Figure 9).

Continuing with the sources of CO₂ in the agricultural area, it should also be mentioned that soil microbial respiration, root respiration, and organic matter decomposition significantly contribute to CO₂ emissions.

While photosynthesis in crops and forests can sequester carbon, unsustainable land management practices often result in agriculture being a net source of CO₂ emissions. Reducing land conversion, improving soil management, and minimizing fossil fuel use are key strategies for lowering the agricultural sector’s carbon footprint.

5.1. Burning Crop Residues

Detecting areas with crop residue burning is performed using satellite imagery (Sentinel-2A and Sentinel-5P) and the Google Earth Engine platform, which allows for estimating the resulting CO₂ emissions [50,51]. In EU countries, the open burning of agricultural residues is prohibited under EU Regulation 1306/2013 [52]. Consequently, open burning practices have declined markedly, particularly in the Baltic states, where the area affected by burning has significantly decreased since their EU accession [53].

5.2. Land Management Practices

Considering the impact of tillage practices on CO₂ emissions, a long-term field study was conducted from 2017 to 2022 to evaluate their effects under varying weather conditions, with a focus on mitigation strategies [54]. The study compared conventional tillage (CT), reduced tillage (RT), and no-tillage (NT) within a crop rotation system. Results showed that CT produced the highest CO₂ emissions, particularly during the summer. In contrast, RT and NT, which retain mulch on the soil surface, significantly reduced CO₂ emissions by approximately 45% and 51%, respectively, compared to CT. The study highlights reduced and no-tillage as effective strategies to mitigate soil CO₂ emissions, supporting EU climate goals.

A similar study [55] conducted over four years investigated CO₂ emissions associated with tillage practices in a wheat–maize cropping system. Results showed that no-tillage (NT) reduced annual CO₂ emissions by 20.5% compared to conventional tillage (CT), with a 28.7% reduction during the maize season but an 8.99% increase during the wheat season. Maize accounted for 70–78% of the total soil CO₂ emissions, and its emission intensity was reduced by 35.9% under NT relative to CT. Furthermore, a study [56] revealed that zero tillage and chisel plow tillage significantly reduced CO₂ emissions compared to conventional plow tillage.

In Mediterranean maize cultivation under low water input management, a study [57] revealed that minimum tillage (MT) significantly reduced CO₂ emissions from soil bacterial activity compared to conventional tillage (CT) using moldboard plowing. In this context, cumulative CO₂ emissions were reduced by approximately 30% during the three months following autumn plowing and by about 28% during the spring–summer growing season. Notably, these reductions were achieved without compromising maize yields.

5.3. Microbial Soil Respiration

Heterotrophic respiration, the decomposition of soil organic matter by microorganisms, is a key process driving soil carbon emissions. Soil CO₂ emissions are influenced by both biological and environmental factors, with temperature and moisture playing particularly critical roles. Rising soil temperatures enhance enzymatic activity, thereby accelerating the decomposition of organic matter and increasing root respiration. This temperature—driven increase in soil respiration can intensify atmospheric CO₂ concentrations, reinforcing climate warming through a self-reinforcing process [58].

Another environmental factor that influences soil CO₂ emissions is soil organic matter. Elevated levels of soil organic matter provide a larger carbon substrate for microbial decomposition, potentially resulting in higher CO₂ emissions when environmental conditions promote respiration [59]. For example, the most significant source of soil-derived CO₂ emissions in Europe is the drainage of peatlands (organic soils). Nearly half of the total soil carbon stock in the EU-27 is concentrated in Sweden, Finland, and the United Kingdom, largely due to their extensive peatland areas. Ireland, Poland, Germany, Norway, and the Baltic states also have large areas of organic soils [60].

A recent model-based study [61], supported by empirical data, estimates that global heterotrophic respiration has risen by about 2% per decade since the 1980s. Under a worst-case emissions scenario, the model projects a 40% increase by the end of the 21st century, with the Arctic region showing the most pronounced rise.

Another study [62] investigated how different land uses (upland fields, rice paddies, and woodlands) affect the rate and carbon isotopic composition (δ¹³CO₂) of soil-respired CO₂. Through long-term soil incubation and aggregate fractionation, the authors observed that both CO₂ emissions and their δ¹³C values declined exponentially over time. The highest respiration rates were recorded in woodland soils, likely due to a higher availability of carbon substrates for microbial activity. A positive correlation between the δ¹³C of respired CO₂ and microbial biomass indicated a strong link between microbial activity and isotopic signatures. These results suggest that soil respiration and its isotopic characteristics respond in complex, land-use-dependent ways to warming, influenced by both soil type and microstructural properties.

The influence of nitrogen fertilization and native soil organic matter on CO₂ emissions under different climatic conditions was investigated using a two-year field experiment in contrasting upland cropping systems representing warm and cold climates [63]. To trace the sources of CO₂ emissions, ¹³C-labeled urea was applied at 0%, 50%, 100%, and 200% of the Korean recommended nitrogen rates. Red pepper was grown during the warm season with 90 kg N ha⁻¹, and garlic during the cold season with 250 kg N ha⁻¹. In the warm season, CO₂ emissions and urea-derived CO₂ increased with higher nitrogen levels and warmer temperatures, likely due to enhanced microbial activity and root respiration. In contrast, both total and urea-derived CO₂ emissions were minimal and unaffected by nitrogen levels in the cold season.

The impact of three organic amendments (chicken manure, milorganite, and dairy manure) applied at four rates (0, 168, 336, and 672 kg N ha⁻¹) on soil CO₂ emissions was evaluated [64]. The results showed that soil CO₂ emissions were significantly influenced by both amendment type and application rate, with chicken manure and milorganite producing higher emissions than dairy manure. Furthermore, the type and rate of organic amendments had a greater effect on CO₂ emissions than environmental factors such as air/soil temperature and rainfall.

Concluding, sustainable land management practices (reduced tillage, elimination of residue burning, optimized nitrogen and organic amendment use) play an important role in mitigating soil-derived CO₂ emissions from agricultural systems. Climate factors like soil temperature and moisture strongly affect soil respiration rates, highlighting the need for context-specific mitigation. Peatland drainage remains a key CO₂ hotspot, requiring targeted management. Integrating these strategies is essential for reducing agriculture’s carbon footprint and enhancing adaptation to climate change.

6. Methane Emissions from Cropping Systems and Livestock

6.1. Emissions from Cropping Systems

The main source of CH₄ in agriculture is paddy fields, with global emissions estimated at around 31–280 Tg yr⁻¹, accounting for approximately 10–20% of anthropogenic CH₄ emissions. The wide range reflects variability due to different estimation methods, geographical distributions, water management practices, and rice cultivars [65].

CH₄ is produced through several chemical processes that start with organic matter, mediated by methanogenic (anaerobic) bacteria. The resulting methane is then released via diffusion (the slow movement of molecules from soil pores to the surface), ebullition (the release of methane bubbles into the atmosphere), or plant-mediated transport (the movement of methane from soil through plant roots and stems) [66]. Alternatively, it can be oxidized to CO₂ by methanotrophic bacteria (Figure 10) [18,66]. Regarding environmental factors, daytime emissions tend to be higher than nighttime emissions and also increase with elevated CO₂ levels [67].

CH₄ emissions from rice fields depend on several factors, including soil characteristics, plant traits, environmental conditions, and agricultural practices [67]. A high level of organic matter (manure, crop residues) provides carbon substrates for methanogens, thereby generally increasing methane emissions. In contrast, the addition of biochar has been shown to reduce CH₄ emissions [68]. Methanogenic microbial activity is also strongly influenced by soil pH and redox potential [69]. Additionally, different rice cultivars can emit varying amounts of methane due to physiological differences.

Fertilizers can either stimulate or inhibit the activity of methanogens and methanotrophs. For example, the use of organic fertilizers and the incorporation of rice straw into the soil tend to increase CH₄ emissions, whereas chemical fertilizers may have a lower impact. A study [69] found that the application of phosphorus (P) and potassium (K) fertilizers significantly reduced methane emissions from rice paddy soils. Furthermore, the combined application of nitrogen, phosphorus, and potassium (N + P + K) fertilizers was shown to reduce CH₄ emissions per unit of grain yield in both dry and wet seasons (6.43 kg CH₄ per Mg of grain in the dry season and 83.57 kg CH₄ per Mg in the wet season).

Considering the necessity to reduce CH₄ emissions from paddy rice cultivation, a study [67] evaluated the impact of various organic amendments on CH₄ release. The treatments were composed of control, blue-green algae (BGA), Azolla, farmyard manure (FYM), green leaf manure (GLM), BGA + Azolla, FYM + GLM, BGA + Azolla + FYM + GLM, vermicompost, and decomposed livestock manure. Among these, the combination of BGA and Azolla achieved the highest reduction in CH₄ emissions (37.9% compared to the control), followed by BGA alone. The findings demonstrate that biofertilizer application represents a viable and effective approach to mitigating CH₄ emissions in rice cultivation.

In addition, among biofertilizers, purple nonsulfur bacteria (PNSBs) are notable for their ability to reduce methane emissions in rice cultivation. For example, a study [70] demonstrated that Rhodopseudomonas palustris strains TN114, PP803, and TK103 reduced total methane emissions by 24–48% in organic and saline paddy soils, respectively, compared to those where chemical organic fertilizers were applied.

Given the increasing importance of reducing CH₄ emissions from paddy fields, agronomists should prioritize the evaluation of water management strategies, fertilization regimes, crop rotation systems, and the selection of low-emission rice cultivars as effective mitigation approaches [71].

Methane estimation using conventional methods has become laborious, time-consuming, and, to some extent, inaccurate. Recently, to overcome these limitations, modern technologies based on remote sensing have been adopted [72,73]. Furthermore, to facilitate the adoption of effective reduction measures, models for estimating emissions have been developed. In this context, empirical models have been developed based on variables such as soil organic carbon, pH, water management, application of organic amendments, and crop yield [74,75,76].

Furthermore, Nikolaisen and colleagues [77], relying on accepted methodologies, compared existing models across different global regions, assessing their performance and limitations. The study concludes that existing empirical models are adequate for predicting methane emission trends but are not reliable for estimating the magnitude of emissions. These models often either underestimate or overestimate emissions, with correlation values varying significantly. To improve emission predictions, the authors suggest that future models incorporate site-specific variables such as soil texture, planting methods, cultivar types, and growing seasons, which significantly influence emissions.

In conclusion, paddy fields are a major source of CH₄ emissions, primarily driven by methanogenic activity under anaerobic conditions. Emissions are amplified by high organic inputs but can be effectively mitigated through improved water and fertilizer management, the use of low-emission rice cultivars, and biofertilizers. Balanced NPK fertilization and alternative crop rotations further help reduce CH₄ intensity. Given the difficulty of direct measurements, empirical and remote-sensing models play a key role in estimating emissions and informing mitigation strategies in rice systems.

6.2. Livestock Emissions

Livestock emissions arise from feed production, enteric fermentation, manure management, and land-use change, contributing about 7.1 Gt of CO₂e annually, or 14.5% of global anthropogenic GHG emissions. Approximately 30% of global methane emissions come from enteric fermentation [78]. Cattle account for almost 77% of these emissions, while buffalo and small ruminants contribute significantly less, 13.55% and 9.52%, respectively [79].

6.2.1. Enteric Fermentation as Methane Source

Enteric fermentation is a natural digestive process in ruminant animals (cattle, goats, sheep, buffalos), during which the feed is broken down and fermented by microbes in their digestive system. In addition to producing energy and protein, this process also generates CH₄, which is primarily released through burping [79].

Methanogenesis in ruminants is a complex biochemical process by which methanogenic archaea produce CH₄ from substrates derived primarily from the fermentation of feed. This process has been comprehensively reviewed by Beauchemin and colleagues [80].

In summary, within the rumen, methanogens primarily convert H₂ and CO₂ into methane via hydrogenotrophic methanogenesis, alongside competing microbial processes, such as sulfate reduction, nitrate reduction, and fumarate reduction that also utilize hydrogen. These competing pathways help regulate hydrogen levels and shape the overall fermentation pattern [80,81]. A schematic representation of this process is presented in Figure 11.

Several factors affect CH₄ emissions from ruminants, such as feed intake levels [82,83], the type of carbohydrates in the diet [84], the method of feed processing, the inclusion of lipids or ionophores, and modifications to the rumen microbial community [85].

Furthermore, several studies [86,87,88] identify seaweeds as a potential dietary strategy for reducing CH₄ emissions from ruminants.

For example, red seaweeds such as Asparagopsis taxiformis and A. armata contain bioactive compounds capable of reducing enteric CH₄ emissions in ruminants by over 90%, and in some cases up to 99%. However, effectiveness depends on season, species, metabolite content, and animal type, while large-scale application is constrained by production, compound stability, and potential impacts on rumen health [87].

Adjusting these factors through targeted dietary and management interventions can help lower methane emissions and contribute to more sustainable livestock production (Table 2).

Furthermore, CH₄ emissions from ruminants vary a lot between species, breeds, and production conditions. A study [88] summarizing current knowledge on CH₄ production from ruminants found that dairy cows are among the highest emitters, with values ranging from 151 to 497 g day⁻¹ (lactating cows: 354 g day⁻¹; dry cows: 269 g day⁻¹; heifers: 223 g day⁻¹). Mature beef cows follow, with emissions ranging from 240 to 396 g day⁻¹, while beef cattle overall emit 161–323 g day⁻¹. Sheep produce much lower CH₄, Suffolk sheep producing 22–25 g day⁻¹. The study also highlighted breed differences within species and the influence of grazing management on emissions; for example, heifers grazing fertilized pasture emit 223 g day⁻¹, compared to 179 g day⁻¹ on unfertilized pasture.

Another study [89] found that CH₄ emissions in dairy cows are influenced by age, with levels peaking in mid-life. Similarly, in Brown Swiss cows, this trend cannot be directly linked to changes in intake, digestion, or chewing activity; however, the corresponding age-related pattern in fiber digestibility suggests it may contribute to the observed emissions pattern.

Also, dietary protein content plays a crucial role in shaping nitrogen excretion patterns and the resulting greenhouse gas (GHG) emissions during manure storage. In this regard, a study [90] demonstrated that lowering the dietary protein content of early-lactating cows reduced N₂O emission rates in most manure types, but increased CH₄ emissions from urine-rich slurry. Consequently, dietary manipulation emerges as an effective strategy for mitigating the environmental impact of livestock production, particularly in terms of reducing nitrogen losses.

In conclusion, enteric CH₄ emissions from ruminants are influenced by diet, feed processing, and animal type. Effectively reducing emissions requires an integrated approach combining strategic feeding interventions, additives (Table 2), genetic selection, and health management, enabling sustainable livestock production without compromising productivity or welfare.

Table 2. Strategies for mitigating CH₄ emissions in ruminant livestock.

Improve Feeding Strategies
Forage quality	Adjusting forage quality and concentrate-to-forage ratio can reduce CH4 by up to 70%; younger/high-quality forage increases propionate and reduces H2 for methanogenesis.	[91,92]
	Inclusion of legumes improves forage quality; tannin-containing legumes inhibit rumen fermentation. High alfalfa (78%) lowers CH4 ~10%, moderate (40%) has no effect.	[93]
	Maize silage lowers CH4 in dairy and cattle.	[94]
Feed additives
Seaweeds	Asparagopsis taxiformis reduces CH4 up to 99% (bromoform inhibits methanogenesis); health concerns with heavy metals.	[95]
	Pelleted Asparagopsis in beef diets reduces CH4 ~37.7%.	[96]
	Red, brown, and green seaweeds contain polysaccharides altering rumen microbes and CH4 emissions.	[97]
Bee propolis extracts	Red propolis reduces CH4 in ewes by modulating rumen fermentation.	[98]
Saponins (glycosides)	Decrease methanogenic archaea and protozoa, reducing CH4.	[99]
Ionophores (antibiotics)	Monensin, lasalocid, narasin, and salinomycin reduce H2 available for methanogens; commonly used in beef diets.	[100]
Yeast	Alternative to ionophores (monensin); modulate rumen microbiome and fermentation, lowering CH4.	[101,102]
Organic acids	Formic, fumaric, malic acids and salts; alfalfa + fumaric acid enhances fermentation and reduces CH4.	[102,103]
3-nitrooxypropanol (3-NOP)	Specific methanogenesis inhibitor; long-term reduction in dairy cows (~21% daily CH4).	[104]
Nitrate (NO3−)	Alternative H2 sink; reduces CH4 ~13.9–30%; caution due to nitrite toxicity risk.	[105]
Genetic breeding
	Selective breeding for low-CH4 cows; Nordic Methane Index targets ~20% reduction.	[106,107]
Improve animal health
	Enhances digestion efficiency, reduces CH4; vaccination trials (sheep) inhibit methanogens; further research needed.	[108,109]

Table 2. Strategies for mitigating CH₄ emissions in ruminant livestock.

Improve Feeding Strategies
Forage quality	Adjusting forage quality and concentrate-to-forage ratio can reduce CH4 by up to 70%; younger/high-quality forage increases propionate and reduces H2 for methanogenesis.	[91,92]
	Inclusion of legumes improves forage quality; tannin-containing legumes inhibit rumen fermentation. High alfalfa (78%) lowers CH4 ~10%, moderate (40%) has no effect.	[93]
	Maize silage lowers CH4 in dairy and cattle.	[94]
Feed additives
Seaweeds	Asparagopsis taxiformis reduces CH4 up to 99% (bromoform inhibits methanogenesis); health concerns with heavy metals.	[95]
	Pelleted Asparagopsis in beef diets reduces CH4 ~37.7%.	[96]
	Red, brown, and green seaweeds contain polysaccharides altering rumen microbes and CH4 emissions.	[97]
Bee propolis extracts	Red propolis reduces CH4 in ewes by modulating rumen fermentation.	[98]
Saponins (glycosides)	Decrease methanogenic archaea and protozoa, reducing CH4.	[99]
Ionophores (antibiotics)	Monensin, lasalocid, narasin, and salinomycin reduce H2 available for methanogens; commonly used in beef diets.	[100]
Yeast	Alternative to ionophores (monensin); modulate rumen microbiome and fermentation, lowering CH4.	[101,102]
Organic acids	Formic, fumaric, malic acids and salts; alfalfa + fumaric acid enhances fermentation and reduces CH4.	[102,103]
3-nitrooxypropanol (3-NOP)	Specific methanogenesis inhibitor; long-term reduction in dairy cows (~21% daily CH4).	[104]
Nitrate (NO3−)	Alternative H2 sink; reduces CH4 ~13.9–30%; caution due to nitrite toxicity risk.	[105]
Genetic breeding
	Selective breeding for low-CH4 cows; Nordic Methane Index targets ~20% reduction.	[106,107]
Improve animal health
	Enhances digestion efficiency, reduces CH4; vaccination trials (sheep) inhibit methanogens; further research needed.	[108,109]

6.2.2. Manure as Methane Source

In addition to CH₄ emissions produced directly by ruminants, another significant source is manure. CH₄ from manure results from the anaerobic decomposition of organic materials in storage systems where oxygen availability is limited. The volume of CH₄ generated is influenced by factors such as the quantity and type of manure, the employed manure management practices, storage conditions, and climatic conditions [110].

For example, a study [111] demonstrated that the type of livestock manure significantly influences CH₄ emissions. In this study, six types of livestock manure (cow, buffalo, goat, rabbit, chicken, and duck) were analyzed over an 8-week period to determine CH₄ production. The results showed the following order of methane emissions (in mg g⁻¹): rabbit manure (2.70) < goat manure (6.01) < chicken manure (17.88) < cow manure (20.32) < buffalo manure (21.93) < duck manure (97.99). These differences were attributed to factors such as the animals’ diet, physiological status, and manure management practices.

Another study [110] examined temperature effects on CH₄ emissions from liquid dairy manure. Under summer conditions, CH₄ production started after ~1 month, reaching 0.148 kg CH₄ kg⁻¹ VS (volatile solid) over 40 weeks. In winter, emissions were much lower, peaking at 0.0011 kg CH₄ kg⁻¹ VS over 20 weeks. The differences are due to temperature: higher summer temperatures enhance microbial activity and volatile solids decomposition, increasing CH₄, while lower winter temperatures suppress microbial metabolism and CH₄ production.

According to a study conducted in Romania [112], sheep manure emits significantly more greenhouse gases per unit area than cattle manure. Specifically, sheep manure produces approximately 0.83 tonnes of CH₄ and 61.3 tonnes of CO₂ per year, while cattle manure emits about 0.185 tonnes of CH₄ and 4.7 tonnes of CO₂ annually.

Table 3. Strategies for mitigating CH₄ emissions from manure.

Control Measure	Effects	Ref.
Anaerobic digestion	Manure in sealed digesters produces CH4 (biogas) for renewable energy; biochar addition can increase CH4 yield up to 80%; ciprofloxacin can inhibit CH4 production in hen manure.	[113,114,115]
Composting	Aerobic composting reduces CH4 by altering nutrients and microbial activity; biochar (cornstalk, bamboo, woody, coir) further reduces CH4; cornstalk biochar reduced CH4 by 26.1%.	[116,117]
Manure covering	Reduces CH4 emissions; polyethylene cover lowers pig manure CH4 by 88%; straw reduces CH4 by 26–50%.	[118]
Solid–Liquid separation	Mechanical separation divides manure into solid (organic matter) and liquid (nutrients); screen size affects CH4 emissions.	[119,120]
Lower storage temperature	Higher temperatures increase CH4 due to faster microbial activity and organic matter degradation.	[121]
Manure acidification	Adding acids (H2SO4, HCl, HNO3, H3PO4) lowers pH, inhibiting methanogens; CH4 reductions: 46–96% (pig slurry), 67% with 17.1 kg H2SO4/m3, pH 5.5 → 95–99% (pig)/65–99% (cattle).	[122,123,124,125]
Additives	CaSO4 reduces CH4 by 63% (higher than H3PO4 54%, lower than H2SO4 91%); polyphenols + NaF reduce CH4; commercial additives like SOP LAGOON also effective.	[126,127,128]

summarizes key strategies used to mitigate CH₄ emissions from livestock manure, spanning biological, chemical, and physical approaches and reflecting the diversity of technologies applicable across different manure management systems.

In conclusion, the effectiveness of CH₄ mitigation strategies is highly dependent on site-specific factors (manure composition, storage conditions), so tailored approaches that combine multiple methods could be adopted. Finding efficient additives may represent a new challenge, the resolution of which could contribute to CH₄ emission reduction. However, the identification of a method that is easy to implement yet effective largely depends on farm conditions and available resources.

In this regard, the most accessible and efficient methods are aerobic composting (combined with different types of biochar for increased effectiveness) and manure covering with various materials. Both methods are accessible, do not require large infrastructure investments, and can result in significant methane emission reductions, making them effective short- to medium-term solutions.

7. Nitrous Oxide Emissions from Agricultural Practices

Agricultural N₂O emissions primarily originate from the application of fertilizers and manure. Once added to the soil, these nitrogen sources undergo a series of microbially mediated processes, including the mineralization of organic matter, nitrification, and denitrification, which ultimately lead to the production and release of N₂O (Figure 12) [34,35,129,130].

N₂O emissions from soils are influenced by multiple factors related to soil properties and management practices (Figure 13) [32,131,132,133,134,135,136,137,138,139,140]. Soil properties such as moisture, texture, temperature, and pH, along with microbial activity, play critical roles in regulating N₂O emissions [32,131,132,133,134,135]. Management practices, including fertilizer application, tillage, residue handling, and irrigation, significantly influence these emissions by altering soil nitrogen availability and microbial processes [135,136,137,138,139,140].

Effective strategies for reducing agricultural N₂O emissions must integrate both soil properties and management practices, including their timing (Figure 14). These factors should be evaluated not only independently but also in combination, as their interactions significantly influence N₂O emission dynamics. Subsequent sections detail key mitigation strategies for N₂O emissions, as developed and applied by experts across various regions.

7.1. Fertilizers—Types, Application Rates, Timing

A recent study [136] emphasized the need for year-round monitoring and adaptive nitrogen management to mitigate N₂O emissions in semi-arid agroecosystems. Over a three-year canola–wheat rotation, applying the 4R nutrient strategy (Right source, Right rate, Right time, Right place) with reduced N rates and enhanced-efficiency fertilizers lowered cumulative N₂O emissions by 57% without affecting yield, mainly by improving nitrogen use efficiency and limiting emissions under high soil moisture conditions.

The type and rate of nitrogen fertilizer strongly affect N₂O emissions in sugarcane systems [141]. Both ammonium nitrate and urea caused emission pulses, but with different timing and intensity: ammonium nitrate produced rapid and high emissions within a day of application, while urea led to delayed peaks after several days. Emissions from ammonium nitrate increased linearly with N rate, whereas urea showed a non-linear response, peaking near 114 kg N ha⁻¹.

Another study [142] indicated that calcium ammonium nitrate (CAN) tends to reduce both ammonia volatilization and N₂O emissions compared to urea, making it a preferred nitrogen source in some sugarcane systems. Furthermore, switching from calcium ammonium nitrate (CAN) to urea-based fertilizers, particularly those stabilized with urease and nitrification inhibitors, proved to be an effective mitigation strategy for reducing N₂O emissions in wet, temperate grassland systems, with emission factors as low as 0.25% [143].

N₂O emissions from sugarcane fields increased sharply with higher nitrogen application rates [144]. Peak emissions occurred within four weeks of fertilization, especially at 500 kg N ha⁻¹ under warm and moist soil conditions. Reducing the rate to about 340 kg N ha⁻¹ maintained yield while cutting N₂O emissions by over 65%, demonstrating the strong mitigation potential of optimized nitrogen management.

In addition, a study [145] presents findings on the impact of replacing mineral fertilizers with organic amendments on GHG emissions, showing that while this substitution significantly reduces N₂O emissions, it simultaneously increases CH₄ and CO₂ emissions, leading to a net increase in GWP.

A study in North-West Germany [146] compared N₂O emissions from winter wheat fields fertilized with urea (U), ammonium sulfate (AS), and calcium ammonium nitrate (CAN) at 220 kg N ha⁻¹. All fertilizers significantly increased emissions compared with the unfertilized control, with cumulative losses following the order U > AS > CAN (0.11–0.28% of applied N). Among them, CAN appeared most effective in minimizing N₂O emissions.

Furthermore, slow-release fertilizers (

Table 4. Effectiveness of controlled/slow-release fertilizers in reducing N₂O emissions across cropping systems.

Product	Crop/Details	Effects	Refs.
Slow-release fertilizer + cyhalofop-butyl	Rice paddies	Lowest cumulative N2O emissions and highest yield among all treatments; inhibits nitrification in paddy soils.	[147]
Controlled-release coated urea (CRCU)/calcium nitrate (CRCN)	Soybean (after rice)	14–41% lower N2O emissions vs. ammonium chloride; effective even at reduced N rates.	[148]
Polymer-coated urea (PCU)	Potato	Increases N availability but may raise N2O emissions when nitrate leaching risk is low.	[149]
Controlled-release fertilizer (CRF) vs. ammonium sulfate (AS)	Temperate soils	CRF soils emitted less N2O; controlled nutrient release reduced emission peaks.	[150]
Controlled-release fertilizer (CRF) vs. urea	Wheat	29–66% reduction in N2O; inhibits nitrification processes; stable under high CO2 conditions without yield loss.	[151]
Biochar-based CRF	Leaching columns	7–66% reduction in N2O emissions and lower nitrate leaching.	[152]

) can reduce N₂O emissions by releasing nitrogen more gradually, thereby minimizing nitrogen losses and lowering peak emissions compared to conventional fertilizers.

7.2. Soil Amendments—Biochar

Biochar is a valuable soil amendment for reducing N₂O emissions through its effects on soil structure and microbial nitrogen cycling, especially denitrification [153].

Studies have demonstrated the potential of biochar to mitigate N₂O emissions from agricultural soils. In energy cane cultivation, biochar application (5 g kg⁻¹ soil) reduced N₂O emissions by 56% with N fertilization alone and by 41% when combined with vinasse, without affecting yield [154]. Similarly, in wheat fields, biochar applied at 5–10 Mg ha⁻¹ together with urea (150 kg N ha⁻¹) decreased N₂O emissions by 27–35%, mainly due to improved ammonium (NH₄⁺) retention, which limited nitrification and N₂O production [155].

A controlled 40-day incubation study [156] examined how soil pH affects the ability of biochar to mitigate N₂O emissions. Biochar alone significantly reduced N₂O emissions in acidic vegetable soil by 47.6% and by 20.8% when combined with nitrogen fertilizer. Its application also raised soil pH across all soil types by 1.43–1.56 units in acidic, 0.57–0.70 in neutral, and 0.29–0.37 in alkaline soils, indicating that biochar’s mitigation effect is strongest under acidic conditions.

A three-year study [157] assessed how biochar application rate and frequency affect soil N₂O emissions in a wheat–maize rotation. Biochar significantly reduced emissions, with annual applications of 8 and 12 Mg ha⁻¹ decreasing N₂O by 31–56% compared with the control. In contrast, a single 12 Mg ha⁻¹ application showed no lasting effect during 2020–2022, indicating that mitigation declines without reapplication. Modeling suggested that the inhibitory effect of one-time biochar application lasts about 1.77 years.

Overall, biochar demonstrates strong potential to reduce N₂O emissions by improving soil properties and microbial processes. However, studies indicate that regular reapplication is necessary to sustain these benefits over time.

7.3. Nitrification Inhibitors

Nitrification inhibitors (NIs) have been recommended by the IPCC [158] as an effective strategy to mitigate nitrous oxide (N₂O) emissions. A variety of nitrification inhibitors (NIs) and their specific applications have been reviewed by Malyan and co-workers [159].

Among these, 3,4-dimethylpyrazole phosphate (DMPP) is the most widely used in Europe due to its high efficiency, low application rate, and minimal ecotoxicity [160].

A study [161] evaluated the effectiveness of a DMPP nitrification inhibitor in reducing N₂O emissions when combined with various alkaline amendments: quicklime (CaO), chicken manure (CM), cow dung (CD), and biochar (BC) on acid soils. It was found that DMPP significantly reduced N₂O emissions when combined with various alkaline amendments, with reductions ranging from 3.3% to 60.2%. The highest mitigation effect occurred with the CaO + DMPP treatment, due to reduced activity of ammonia-oxidizing bacteria (AOB).

The NIs, 3,4-dimethylpyrazole phosphate (DMPP) and 3-methylpyrazole 1,2,4-triazole (Piadin), were investigated for sweet corn, and it was found to reduce N₂O emissions. Additionally, applying NI-coated urea at 20% reduced nitrogen rates decreases cumulative N₂O emissions by 51% without reducing the yield [162].

Corn field experiments demonstrated that applying urea combined with the NI dicyandiamide (DCD) at 170 kg urea ha⁻¹ + 20 kg DCD ha⁻¹ reduced N₂O emissions to approximately 3% of those from standard urea application, with emissions comparable to the unfertilized control and no impact on grain yield; in contrast, controlled-release fertilizer (LP-30) reduced emissions relative to urea but was less effective than the urea + DCD treatment, making the latter the most efficient mitigation strategy tested [163].

These studies sustain that NIs are highly effective in mitigating N₂O emissions, especially when combined with soil amendments or reduced nitrogen rates, without affecting crop yields.

7.4. Crop Residue Incorporation

Incorporating crop residues into the soil typically increases N₂O emissions by an average of 43% compared to residue removal. This is because residues provide nitrogen and readily decomposable carbon, which enhance microbial activity, particularly the nitrification and denitrification processes responsible for N₂O production [139].

Evaluation of N₂O emissions from crop residues is very challenging because it depends on various factors, including soil properties (clay content, aeration, pH), climatic conditions [139].

A study [164] describes that incorporation of mature crop residues (soybean: C/N = 75; corn: C/N = 130) led to rapid nitrogen immobilization, reducing N₂O emissions in high-carbon (silty clay) soils. In contrast, in low-carbon (sandy loam) soils, residue addition also caused nitrogen immobilization, but under moderate freeze–thaw (FT) conditions, N₂O emissions increased, likely due to early stimulation of microbial activity by the added carbon. These findings highlight that residue quality and soil carbon content strongly influence the impact of FT cycles on N₂O emissions. Therefore, incorporating mature crop residues can be an effective strategy to reduce FT-induced N₂O emissions, particularly in carbon-rich soils, by promoting mineral nitrogen immobilization.

7.5. Tillage and Irrigation Management

Tillage influences N₂O emissions primarily by altering soil physical conditions, microbial activity, and nitrogen cycling processes [32].

No-tillage (NT) and reduced tillage (RT) practices generally lower N₂O emissions compared with conventional tillage (CT). For example, NT reduced emissions by 51.1% in maize [165], while RT lowered emissions by 15–40%, likely due to reduced easily mineralizable soil components [166]. Combining NT with organic amendments, such as liquid pig manure, further decreased N₂O emissions compared to CT and chemical fertilizers in soybean systems, with reductions ranging from 20% (no fertilizer) to 35.7% (hairy vetch) [167].

However, NT does not always reduce N₂O emissions, as they depend on soil properties, moisture, temperature, residue management, and fertilization. A study in Ontario (2003–2005) showed variable responses: no-till corn had higher emissions in wet years, while tilled soils emitted more in 2005 due to enhanced aeration; soybean fields exhibited consistently low emissions due to limited biological N₂ fixation [168].

Deficit irrigation is another effective mitigation strategy, maintaining optimal soil moisture and reducing prolonged saturation that favors N₂O production [169]. Deficit irrigation reduced N₂O by 17.4% in wheat and 15.5% in maize [170], while moderate and severe deficit irrigation under drip-fertigation in maize decreased emissions by 15% and 40%, respectively, compared to full irrigation [171].

7.6. Crop Rotations and Integrated Nutrient Management

A field experiment evaluated the effects of continuous mineral and organic N fertilization on N₂O emissions in a maize–wheat rotation [172]. Mineral N at 200 kg ha⁻¹ produced 2.71 kg N ha⁻¹ of N₂O annually. Replacing 50% of mineral N with cattle, chicken, or pig manure did not significantly change emissions, whereas a 25% replacement reduced N₂O by 21–38%, mainly during the maize season. These reductions occurred without compromising crop yield, indicating that partial substitution of mineral N with organic manure can effectively mitigate N₂O emissions.

A study [173] evaluated the effect of reduced inorganic N input combined with organic amendments on N₂O emissions in a winter wheat–summer maize rotation. Three treatments were tested: RN (100% recommended N), RN40% + HOM (40% N + homemade organic matter), and HAN (zinc and humic acid-coated urea at full N rate). RN40% + HOM reduced cumulative N₂O emissions by 41% compared to RN and by 20.9% compared to HAN, while maintaining high yields, making it the preferred option.

A two-year on-farm study in northwest Germany [174] assessed the impact of converting from conventional to organic arable farming on N₂O emissions. Two organic rotations were tested: (1) with 25% legumes (grass + clover–winter wheat–winter rye–oats) and (2) with 40% legumes (grass + clover–winter wheat–winter rye–spring field peas–winter rye), compared to (3) a conventional rotation (winter oilseed rape–winter wheat–winter wheat–sugar beet–winter wheat). Two non-cropped systems served as references: (4) extensive grassland and (5) beech forest. The lowest N₂O emissions occurred in grassland (0.3 kg N ha⁻¹yr⁻¹) and forest (0.4 kg N ha⁻¹ yr⁻¹), while organic systems emitted about 0.7 kg N ha⁻¹ yr⁻¹, 66% less than the conventional system (2.1 kg N ha⁻¹ yr⁻¹).

These studies demonstrate that integrating organic inputs or legume-based rotations can significantly reduce N₂O emissions across various cropping systems, without compromising crop productivity.

Overall conclusions that result from the above studies show that various agricultural practices hold significant potential to mitigate N₂O emissions. The most effective strategies include optimized fertilizer management, the use of nitrification inhibitors, biochar application, and organic amendments. Furthermore, integrating diverse crop rotations, adopting conservation or reduced tillage systems, and implementing efficient irrigation management can further contribute to emission reductions. However, the effectiveness of these mitigation approaches depends strongly on local soil characteristics, climatic conditions, and specific cropping systems. Therefore, continuous research, long-term field monitoring, and the adaptation of these practices to regional contexts are essential to achieve sustainable and long-term reductions in greenhouse gas emissions from agriculture, particularly in the context of ongoing climate change.

8. Gaps, Challenges, and Future Perspectives for Reducing Agricultural GHG Emissions

This section presents a comprehensive overview of the challenges associated with greenhouse gas (GHG) emissions from agriculture, highlighting key barriers such as economic constraints and policy issues, existing gaps in scientific knowledge, like measurement limitations and regional variability, and important unanswered questions related to the effectiveness and net impact of mitigation technologies (Figure 15). Understanding these interconnected factors is essential for developing effective strategies to reduce agricultural GHG emissions.

Although mitigation in the agriculture sector is both urgent and important, passing and implementing measures to reduce emissions can be challenging. Thus, a range of barriers exists at various levels—from the farm to the national and even global scale.

8.1. Barriers

Diversity of emission sources is a key challenge in addressing GHG emissions from agriculture. The sector produces GHGs from multiple sources, including enteric fermentation, manure management, soil microbial activity, and land-use changes. This diversity reflects the wide range of biological and management processes involved in agricultural production. Moreover, the variability introduced by different animal species, manure types, farming practices, and climate conditions adds further complexity to the task of managing and mitigating these emissions effectively.

Considering economic constraints, many farmers, particularly those operating small-scale farms, may lack the financial capacity to invest in the infrastructure and technologies required to reduce GHG emissions. The adoption of effective mitigation strategies may be severely constrained in regions where financial resources, institutional support, and technical capacity are insufficient.

Furthermore, knowledge and awareness barriers also pose a challenge to reducing agricultural GHG emissions, showing that insufficient information continues to hinder the adoption of sustainable practices. A significant challenge is the resistance from farmers to adopting new technologies or practices that could reduce GHG emissions. This resistance can stem from several factors, including a lack of awareness about the environmental and economic benefits of such practices, perceived risks, and financial constraints. In some cases, farmers may view new technologies as too costly or too complicated to implement. For instance, a study [175] found that while 30% of farmers were open to adopting smart farming technologies (SFT), others preferred production (21%) or organic farming (49%) approaches to mitigate emissions.

Technical limitations in measuring agricultural emissions create significant uncertainty in evaluating both the effectiveness and long-term permanence of mitigation efforts. Although various mitigation measures are available, their implementation is often constrained by technological and practical challenges. For instance, strategies aimed at reducing manure-related emissions typically require substantial investments in infrastructure, technical expertise, and resources—factors often lacking in many agricultural regions, particularly in developing countries or less technologically advanced areas.

Moreover, commonly used measurement methods are frequently labor-intensive, costly, and prone to inaccuracies due to their sensitivity to variables such as soil conditions, climate variability, and farm management practices [176]. Environmental fluctuations and the limited capacity to capture emissions accurately over time and across spatial scales further reduce the overall precision of these methods.

To address these challenges, researchers have developed various process-based models that simulate soil–plant–atmosphere interactions, enabling the estimation of greenhouse gas emissions under diverse environmental and management conditions. Several such models have been applied in different contexts [177,178,179], each offering specific strengths and limitations. Their accuracy depends heavily on factors such as climate, management practices, and the availability of reliable input data. While some models are better suited to certain crops or greenhouse gases, no single model has proven universally accurate.

To improve model performance and reliability, future research should focus on expanding model applicability, ensuring the use of consistent and high-quality validation data, and refining algorithms to better incorporate key biological and environmental processes.

Policy and regulatory barriers to reducing agricultural GHG emissions include opposition to carbon pricing and the sector’s strong dependence on subsidies, which often have limited mitigation potential. Additional challenges stem from the difficulty of accurately quantifying emissions in a highly dispersed and variable sector, as well as from economic and social conditions that may reduce the effectiveness of policy interventions [180,181].

Furthermore, policy incentives, such as financial rewards or tax reductions, can act as effective motivators for farmers to implement GHG mitigation practices [182]. However, although many countries have introduced regulations targeting agricultural emissions, policy frameworks are often fragmented, and enforcement tends to be inconsistent. Many policies also fail to provide sufficient incentives or support mechanisms for the adoption of mitigation technologies.

Without robust, coherent policies and well-designed incentive structures, agricultural emissions are likely to continue rising, even in the presence of regulatory measures.

8.2. Gaps

Considering the existing gaps related to agricultural GHG emissions (Figure 15), it is important to highlight the lack of precise and consistent data, as well as the difficulties in quantifying indirect emissions, particularly those arising from fertilizer production and land-use change [183].

In addition, current estimation models remain insufficiently developed, with various limitations in their ability to simulate the complex interactions between biological, chemical, and environmental processes involved in GHG emissions [179].

Furthermore, measurement and monitoring uncertainties complicate mitigation efforts, as emissions are highly variable and influenced by factors such as soil and crop types, farming practices [184].

Lastly, incomplete and inconsistent data on livestock emissions, especially from enteric fermentation and manure management, represent another critical challenge in building accurate inventories and informing effective mitigation strategies [185].

Compared to other major agricultural regions, the European Union continues to face technical gaps in reducing agricultural GHG emissions, primarily due to the slow adoption of innovative mitigation technologies. Although strong policy frameworks exist, the adoption of precision agriculture and digital monitoring systems remains slower in many EU member states [186]. For comparison, the United States demonstrates a significantly higher adoption rate of precision agriculture technologies (approximately 70%) largely due to the prevalence of large-scale farms, stronger private investment, and better access to digital and technical infrastructure [187].

8.3. Unanswered Questions

Despite major scientific and technological advances, significant uncertainties and unresolved questions remain regarding agricultural GHG emissions (Figure 15). Critical issues, such as how to measure emissions reliably and affordably on small and medium-sized farms, or whether mitigation technologies (biochar, nitrification inhibitors, feed additives) deliver net reductions, remain unanswered.

The diversity of agricultural systems across the EU further complicates the development of universally effective mitigation strategies. Economic, cultural, institutional, and informational barriers vary widely by context, making it difficult to identify the most limiting factors. Similarly, while agricultural carbon sequestration is often promoted as a key solution, land availability and the long-term sustainability of such practices differ greatly between regions.

These knowledge gaps arise not only from a lack of research but also from the complexity of agricultural systems, variability of local conditions, and the intricate relationships between environmental, economic, and social factors.

8.4. Further Perspectives

The difficulty in finding clear answers lies not in the absence of research but in the challenge of integrating fragmented data, context-specific realities, and evolving scientific understanding into coherent, scalable, and actionable strategies.

To overcome the challenges of reducing GHG emissions from agriculture, future efforts should focus on the following strategies:

(a)

Technological advances: this includes the development of methane inhibitors, biochar amendments, advanced anaerobic digestion, and precision nutrient management to increase mitigation efficiency.

(b)

Integrated mitigation strategies: practices such as conservation agriculture, cover cropping, optimized fertilizer use, and improved manure management can reduce GHGs while enhancing soil health.

(c)

Enhancing soil carbon sequestration: this has the potential to offset a significant portion of CO₂ emissions from agriculture. Practices like agroecology, organic farming, and agroforestry can improve soil carbon stocks, turning farms into carbon sinks.

(d)

Integrated policy frameworks: these should promote sustainable farming practices, incentivize farmers to adopt low-carbon technologies, and provide clear frameworks for measuring and reporting emissions.

(e)

Monitoring technologies: remote sensing, sensors, and modeling tools can provide real-time data on emissions.

(f)

Education and continuous research: these are essential for developing new technologies and practices.

Considering the environmental impacts of GHGs, it is crucial to mitigate emissions from agriculture through innovative practices such as precision nutrient management, improved manure handling, soil carbon sequestration, and the implementation of stringent regulations.

9. Conclusions

The research highlights the significant role of agriculture in GHG emissions both within the European Union (EU) and globally. The primary GHGs from agricultural activities—carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O)—contribute to climate change, emphasizing the need to address agricultural practices in mitigation strategies. EU-level emissions remain high, although existing reduction measures have improved control compared to the global level.

Key EU regulations aim to support emission reductions and broader climate goals, such as climate neutrality by 2050 and a 55% reduction by 2030 relative to 1990 levels. Regulations targeting fertilizers, livestock, and land-use are crucial, but their effectiveness depends on enforcement, innovation in farming practices, and farmer engagement.

GHG emissions can be mitigated through practices such as nitrification inhibitors, balanced fertilization, crop rotations, integrated nutrient management, and soil amendments like biochar. Soil carbon sequestration via sustainable farming can also significantly reduce emissions by capturing carbon in soils [188].

Livestock emissions, particularly CH₄ from enteric fermentation in ruminants, are major contributors. Feed type, forage quality, and additives such as seaweeds, saponins, ionophores, and 3-nitrooxypropanol can reduce methane. Complementary strategies include targeted diets, genetic breeding, and improving animal health and digestive efficiency.

Manure-related CH₄ emissions can be mitigated through anaerobic digestion (potentially with biochar), composting, covering, acidification, and temperature management during storage.

In addition to conventional mitigation practices, such as those presented in detail in the present study, the agricultural sector can also benefit from technological innovations (precision farming tools, emission-monitoring sensors), advisory services that guide farmers in adopting best management practices, and market-based mechanisms, including carbon credits, carbon farming schemes, and payments for ecosystem services, all of which, when combined with proper monitoring, can enhance the effectiveness and scalability of GHG emissions reductions across diverse farming systems.

Despite advancements, many questions remain unresolved, and emission control is not yet fully achieved. Nevertheless, ongoing research contributes to understanding and improving mitigation strategies, supporting the objectives of EU regulations.