Climate-Smart Agricultural Practices—Strategies to Conserve and Increase Soil Carbon in Hungary

Abstract

This review summarizes the role of soil in climate change mitigation and highlights the potential of agricultural practices to support this effort. It provides an overview of methods that enhance soil carbon sequestration and reduce carbon dioxide emissions from soils. After presenting a brief global overview, we focus on how the organic carbon stocks of Hungarian agricultural areas have changed over the past decades, underscoring the importance of climate-smart agricultural practices. We examine how these practices—such as cover crops, conservation tillage, fertilization, crop rotation, regenerative agriculture, and agroforestry—affect soil carbon stocks. While the review draws on global research, its primary focus is on practices applicable in Hungary. The effectiveness and feasibility of these climate-smart agricultural practices depend significantly on local climate, geographical location, and soil conditions. Therefore, we thoroughly analyze the applicability and limitations of each practice within the Hungarian context. In addition, we explore temporal trends to assess how the adoption of certain climate-smart practices has evolved over the past one to two decades. Lastly, we discuss the challenges of implementing the presented practices from economic, policy, regulatory, and human perspectives.

1. Background

Carbon dioxide (CO₂) is one of the main greenhouse gases (GHG), which have both natural and anthropogenic sources and natural sinks. Atmospheric CO₂ concentration remained relatively constant at around 280 ppm for a long time before the Industrial Revolution. However, at the beginning of the 19th century, it began to rise rapidly, exceeding 410 ppm nowadays, and the rate of increase has accelerated [1]. This rise is primarily driven by anthropogenic activities, including the burning of fossil fuels, land use changes, deforestation, and various agricultural practices. Increased CO₂ concentration contributes significantly to global climate change, generating a number of interlinked and interacting processes. Temperatures are rising globally, posing significant challenges to the agricultural sector. Rising temperatures and less precipitation amounts are leading to the desertification of certain areas, resulting in the loss of land area previously suitable for agricultural production [2]. Global climate change is also leading to an increase in the number and length of heatwaves, the frequency of weather anomalies, changes in rainfall patterns, and the frequency of intense rainfall events [3,4], all of which could lead to a reduction in the security of agricultural production and difficulties in meeting the growing food demand. Global warming may lead to a reduction in the area of ice caps, increase in sea levels, increase in number of wildfires, warming of oceans [5], a spatial loss of habitats, and thus a reduction in biodiversity, raising a number of human, ecological, and economic concerns in addition to agricultural concerns. The World Meteorological Organization reported that the year 2024 was the warmest on record, with global average temperatures exceeding 1.5 °C compared to pre-industrial times [6]. Further increases in global temperature may worsen these issues; therefore, along with developing adaptation strategies, it is crucial to reduce further increases in atmospheric CO₂ concentrations and enhance carbon sequestration as strategic objectives for mitigating climate change.

Soils worldwide are considered the largest carbon reservoirs, storing more carbon (C) than the total amount found in aboveground biomass and the atmosphere. However, alongside the increase in atmospheric CO₂ concentrations, soil organic matter (SOM) stocks are gradually declining [7]. In addition, changing climatic conditions and rising temperatures accelerate the release of soil-stored carbon into the atmosphere, further increasing atmospheric CO₂ levels and exacerbating soil carbon loss [8]. The carbon content of soils influences their functions, fertility, structure, and water management properties, and thus plays a crucial role in efficient agricultural production [9,10] and climate change mitigation [9,10,11,12]. Since successful and sustainable crop production is fundamental to food security, preserving soil organic carbon stocks is essential not only for climate protection but also for improving soil health to ensure stable agricultural productivity [13]. Recognizing these links in the second half of the 20th century, there has been an increasing focus on identifying and investigating anthropogenic sources of CO₂ emissions.

With the establishment of the Intergovernmental Panel on Climate Change (IPCC) in 1988, a dedicated international organization was created to monitor climate change, compile and synthesize scientific research, inventory GHG emission sources, and quantify emissions. A standardized methodology was developed to assess national emissions by sector, ensuring consistency in reporting and comparison across countries [14]. Over the past 25–30 years, numerous international agreements, conventions, and regulatory frameworks have been implemented at both the global and European levels to mitigate CO₂ emissions and address anthropogenic climate change.

The Rio Earth Summit, organized by the United Nations in 1992, was one of the most important environmental events of its time, which aimed to bring global environmental challenges together at the international level. Although the Earth Summit did not establish direct requirements for agricultural production, it marked the beginning of global climate negotiations [15]. The Paris Agreement, adopted in 2015, set a key objective of limiting global warming to below 2 °C through carbon neutrality. While the agricultural sector was not explicitly assigned binding emission reduction targets, the agreement holds significant implications for agriculture. It already recognized that climate change poses a global threat to food security [16,17], highlighting the need for sustainable agricultural practices and strategic planning to enhance the resilience and adaptability of the sector.

In 2019, the European Commission presented the European Green Deal [18], a comprehensive climate strategy for the European Union, that prioritizes the promotion of sustainable agriculture (Farm-to-Fork strategy [19]) to increase SOM, carbon sequestration, and afforestation [20]. The European Commission also presented the “Fit for 55” package [21] in 2021, which was adopted by the European Parliament in 2023. It sets sectoral guidelines and standards for carbon sequestration and CO₂ emission reductions. Achieving the reduction target requires a contribution from all sectors, including agriculture. This will necessitate the EU to sequester 310 million tons of CO₂-equivalent carbon from LULUCF sector (Land Use, Land Use Change, and Forestry) by 2030, and the entire agricultural sector to become carbon neutral by 2050. It can be seen that, alongside afforestation, increasing the carbon sequestration capacity of soils and exploiting their carbon sequestration potential is one of the new challenges of the 21st century [22].

Traditional farming practices result in significant loss of soil organic carbon, so there is a need for wider adoption of newer, low-carbon farming practices. At the level of agricultural production, there are three main options for reducing atmospheric CO₂ concentrations: (1) reducing the emissions from agriculture, (2) increasing the carbon sequestration capacity of soils, and (3) replacing fossil fuels with biofuels. A key objective is to increase the carbon content of soils, and to store carbon in the soil in the form of stable humus, thereby contributing to both climate change mitigation goals and predictable agricultural production and food security [23]. To align with these objectives, the concept of climate-smart agricultural (CSA) practices was created. This approach focuses on enhancing the resilience of agricultural systems to the impacts of climate change. It also aims to reduce agriculture’s contribution to climate change by lowering emissions and increasing carbon sequestration, all while ensuring food security is not compromised. Based on FAO guidance, a large number of CSA farming practices have been developed. Seventy-four existing farming practices in Europe with contribution to CSA outcomes were identified by Erekalo et al. [24]. According to their categorization, there are seven groups of practices: “Climate-smart agroecological farming practices for soil improvement”, “Climate-smart fertilization”, “Climate-smart crop protection”, “Climate-smart irrigation management”, “Improved animal husbandry and manure management”, “Climate-smart livestock feed management”, and “Integrated farming practices”. The aim of our recent study was to describe practices that can be preserve and improve soil carbon stock and are highly relevant in the Hungarian agricultural environment.

Hungary has also been affected by global climate change in recent decades. Although annual precipitation has not decreased significantly since 1901, the altered distribution of precipitation has led to longer droughts and an increase in the proportion of high-intensity precipitation events. Over the last thirty years, Hungary has experienced a significant warming. The annual mean temperature is about 1.5 °C higher than the 1991–2020 average. The summer months show an even stronger warming, with an observed increase of about 2 °C [25,26].

The European Union’s emission reduction and carbon sequestration targets must also be met in Hungary, so climate-friendly agricultural practices are becoming increasingly important in this region. Our work aimed to summarize the agricultural practices that could be relevant for soil carbon sequestration and CO₂ emission reduction, with a special focus on practices that have a high potential in Hungary.

2. Methodology

This study aimed to summarize the role of our soils in mitigating climate change and to explore how different agricultural practices can enhance soil carbon content or reduce CO₂ emissions from soils. We aimed to provide a comprehensive overview of climate-smart agricultural (CSA) practices in Hungary, examining their adaptability and the challenges they face in implementation. We used different scientific databases including Web of Science, Google Scholar, and ScienceDirect to prepare the literature review. The key terms we focused on included agroforestry, climate-smart agriculture policies, conservation agriculture, cover crop, nitrogen dilemma, no-till, reduced tillage, regenerative agriculture, and SOC: clay ratio, soil CO₂ efflux, soil CO₂ emission, and soil health indicator. We found the references based on the keywords presented. A total of 187 references were used for the review, of which 168 were scientific publications, 11 were European documents on various agreements (Paris Agreement, The European Green Deel, etc.) or reports, and 8 were some European or national databases. The number of literary sources used, organized by publication year, is illustrated in Figure 1.

For evaluation of climate-smart agricultural practices in Hungary, we used data provided by the Hungarian Central Statistical Office, with a special request for data on cover crops, tillage, and crop rotation, to ensure we had the most current data. For the Hungarian SOC change and SOC: clay ratio maps and tables, we used data from the Hungarian Soil Information and Monitoring Systems and Hungarian DOSoReMI databases.

3. Carbon Balance in Agricultural Soils

3.1. Global Outlook

Soil organic matter consists of a variety of organic compounds and contains approximately 50% carbon [27]. This means that soil is one of the most important carbon pools in the biosphere, holding about 2.5 gigatons (Gt) of carbon. Soil plays a crucial role in the global carbon cycle, acting as both a carbon sink and a carbon emitter [28]. SOM is found in soil in various decomposed forms [29,30,31,32].

In the last centuries, agricultural production has become increasingly intensive. After deforestation and conversion of grasslands to agricultural areas, new areas were developed for crop production, prioritizing productivity over sustainability in response to the rising food demand. As a result of the intensive management and, in many cases, lack of soil cover, global soil organic carbon (SOC) levels on agricultural lands have declined. Estimates suggest that the rate of decline could be as high as 75%, but the extent of this reduction is highly dependent on climate, soil type, and agricultural practices. Globally, approximately 66 to 90 Gt of carbon is lost from soils as a result of agricultural production [3]. Thus, the carbon content of agricultural soils has typically decreased, affecting not only the mobilizable carbon pools but also the stable humus content. However, cultivated soils have the highest potential for carbon sequestration, with a sequestration capacity of about 1.2–3.1 Gt C year⁻¹ [33].

3.2. Estimating SOC Stock in Hungarian Soils Using Different Approaches

In Hungary, SOC stocks have declined in recent decades due to inappropriate soil use and management practices. Using machine learning combined with space–time geostatistics, Szatmári et al. [34] created a series of maps illustrating the changes in SOC stocks in Hungary from 1996 to 2016 [34]. Their mapping campaign relied on SOC data derived from the Hungarian Soil Information and Monitoring System (SIMS). SIMS was established in 1992 with the objective of collecting geographically referenced information on the chemical and biological change of Hungarian soils at 1236 monitoring sites, covering evenly the whole territory of the country. SOC is measured every three years according to the Hungarian standard (MSZ-08-0452:1980) [35]. In Figure 2, a SOC stock change map between 1992 and 2016 is presented based on Szatmári et al. maps, masked with non-agricultural areas from the ecosystem map of Hungary [36]. Note that the map refers to the topsoil (0–30 cm).

In Hungary, different soil types are classified into specific growing area quality classes considering the factors influencing crop production, determining soil fertility, and nutrient supply. These classes are as follows: (1) chernozems, (2) brown forest soils, (3) meadows and alluvial soils, (4) sandy soils, (5) salt-affected soils, and (6) shallow soils. Categories include several soil types with similar properties, based on genetic soil classification [37]. The characteristics of soils and crop production of the different quality classes, which form the basis for the classification, were presented in detail by Antal et al. [37], a brief summary of which is given in

Table 1. Characteristics of growing area quality classes (based on Antal et al. [37]).

Growing Area Quality Classes	Characteristics of Soils	Characteristics of Crop Production, Cultivable Crops
Chernozems	deep humus-rich layer, excellent water and air management, good nutrient supply	the most demanding plant species
Brown forest soils	good nutrient supply, water, and air management	demanding plant species
Meadows and alluvial soils	good nutrient stock but poor nutrient availability, high water holding capacity, poor drainage, heavy textured soils	limited crop choice, significant year effect
Sandy soils	light texture, low colloid content, unfavourable water management, low water holding capacity	low yields, variable yield security
Salt-affected soils	unfavourable chemical and physical properties, extreme water management, high nutrient stock, but low nutrient availability	limited number of cultivable crop species, high yield variability
Shallow soils	shallow topsoil, low water retention, limited nutrient availability	plant species with low water requirements and short growing season

.

Table 2. SOC stocks and SOC stock change in agricultural areas from 1992 to 2016 in Hungary. The rows ‘1992’ and ‘2016’ are the statistics for the SOC stock maps 1992, and 2016, respectively. ‘Change 1992–2016’ are the statistics of the SOC stock change map (Figure 1).

	Growing Area Quality Classes	Area	Min	Max	Range	Mean	Sum
		ha	t ha−1				Mt
1992	Chernozems	1,371,200	14.31	101.93	87.62	57.95	79.46
	Brown forest soils	823,700	9.74	107.43	97.69	43.20	35.58
	Meadows and alluvial soils	1,612,000	12.86	117.05	104.18	57.23	92.25
	Sandy soils	391,100	11.07	95.02	83.95	35.77	13.99
	Salt-affected soils	477,700	14.40	104.43	90.03	61.11	29.19
	Shallow soils	108,400	22.39	81.95	59.55	45.89	4.98
2016	Chernozems	1,371,200	15.64	90.84	75.20	55.11	75.57
	Brown forest soils	823,700	16.55	114.00	97.45	43.96	36.21
	Meadows and alluvial soils	1,612,000	14.61	108.16	93.55	55.70	89.78
	Sandy soils	391,100	9.92	92.15	82.23	35.38	13.84
	Salt-affected soils	477,700	14.59	90.74	76.14	58.98	28.18
	Shallow soils	108,400	23.35	79.20	55.84	45.17	4.90
Change 1992–2016	Chernozems	1,371,200	−43.61	37.64	81.25	−2.84	−3.89
	Brown forest soils	823,700	−24.52	46.27	70.79	0.76	0.63
	Meadows and alluvial soils	1,612,000	−42.80	25.45	68.24	−1.53	−2.47
	Sandy soils	391,100	−25.65	17.52	43.17	−0.39	−0.15
	Salt-affected soils	477,700	−26.40	24.05	50.45	−2.13	−1.02
	Shallow soils	108,400	−32.35	26.49	58.84	−0.72	−0.08

shows the minimum and maximum SOC stock values for these growing area quality classes, highlighting the change from 1992 to 2016, which was calculated from the values of the SOC change map (Figure 1). The growing area quality classes are classified based on the soil-type map for Hungary of the DOSoReMI.hu (Digital, Optimized, Soil Related Maps and Information in Hungary) database [38,39].

In both 1992 and 2016, sandy soils in Hungary had the lowest average organic carbon content in the upper 30 cm layer (35.77 and 35.38 t ha⁻¹, respectively). In contrast, both in 1992 and in 2016, salt-affected soils had the highest average organic carbon stock values (61.11 and 58.98 t ha⁻¹). This may be because the meadow soils with saline subsoil horizons were also classified here. However, during the 25 years studied, the most significant negative changes occurred in chernozems soils and meadow and alluvial soils, resulting in a national carbon loss of 3.89 t ha⁻¹ and 2.47 t ha⁻¹, respectively. This is also of great importance, since more than 60% of agricultural production takes place in these two growing areas.

For the same growing area quality classes, we evaluated the Hungarian agricultural soils on the basis of SOC: clay ratio values. The SOC: clay ratio is one of the most recently used indicators of soil structural quality, developed by Johannes et al. [40]. It classifies soil structure as very good, good, medium, or degraded, depending on whether the SOC: clay ratio is greater than 1:8, between 1:8 and 1:10, between 1:10 and 1:13, or less than 1:13, respectively. To calculate the SOC: clay ratio values for the Hungarian growing area quality classes (

Table 3. SOC: clay ratios in agricultural areas for the Hungarian growing area quality classes.

Growing Area Quality Classes	Area	Min	Max	Range	Mean
	ha	SOC: Clay Ratio
Chernozems	137,1200	0.02	0.65	0.63	0.07
Brown forest soils	823,700	0.02	0.60	0.59	0.05
Meadows and alluvial soils	1,612,000	0.02	0.79	0.77	0.06
Sandy soils	391,100	0.01	1.06	1.05	0.13
Salt-affected soils	477,700	0.02	0.97	0.96	0.07
Shallow soils	108,400	0.02	0.51	0.49	0.05

), we used the SOC content map of Szatmári et al. [41], and clay content map of DOSoReMI.hu database [39,42]. The SOC content was determined according to the Hungarian standard (MSZ-08-0452:1980, 1980). Reference data for both maps are from 1992 and refer to depths 0–30 cm.

Based on average values, the majority of soils in Hungary can be classified as degraded, as shown in Figure 2. Using this method, the sandy soils of the Danube–Tisza and Nyírség regions are classified as soils with good structure, which show the limitations of this classification system, as pointed out also by several studies [43,44]. According to Rabot et al. [45], the degradation threshold must be corrected from 1:13 in order to assess the specific carbon status of a given pedoclimatic region. Mäkipää et al. [46] also found that the SOC and clay content in Europe are much more variable depending on vegetation, soil type, land use, and climate, than the interval for which the indicator was originally developed. Therefore, threshold values must be adapted to regional and local climatic and land use conditions. Figure 3 illustrates that these thresholds are not applicable to Hungarian soils and that specific national thresholds need to be developed for local conditions.

Although the method is not universally applicable for assessing soil structure, the SOC: clay ratio can still provide useful insights under certain conditions, considering its limitations. If it indicates that the soil structure is vulnerable, the cropping practices in the area should be reviewed, and practices aimed at increasing SOC should be adopted [44].

The values presented in this section illustrate the importance of agricultural practices aimed at maintaining soil carbon stocks. However, various management practices can increase carbon stocks over the long term, typically within 10 to 20 years [47,48]. Therefore, the primary goal should be to ensure that different agricultural practices not only promote a rapid uptake of SOM but also increase soil carbon in the form of stable humus [49]. Increasing SOC levels will not only support climate change mitigation goals but also improve agricultural production and food security. The adoption of climate-smart agricultural technologies is essential to achieve these goals. In the following section, the CSA practices that may be relevant in Hungary will be the primary focus.

4. Climate-Smart Agricultural Practices

The greatest carbon sequestration potential of soils is in agricultural areas, but it is essential to use climate-smart agricultural technologies to exploit this potential. The FAO introduced the definition of CSA in 2010 with three principal outcomes: (1) the sustainable increase in agricultural productivity, (2) the enhancement of resilience to climate change, and (3) the mitigation of GHG emissions [50]. Several practices and measures can be used during agricultural production to enhance carbon sequestration, thereby increasing soil carbon stocks and mitigating CO₂ emissions. However, the adaptability of the measures is highly dependent on climatic and geographic conditions or soil type. Therefore, the evaluation of CSA practices should be implemented on national or regional level.

This chapter presents various climate-smart agricultural practices. The most important information is presented in a summary table (

Table 4. Advantages and disadvantages of climate-smart agricultural practices.

Climate-Smart Agricultural (CSA) Practice	Advantages	Disadvantages
Cover crops [51,52,53,54,55]	enhance productivity and biodiversity; primary carbon source; improve soil structure; reduce erosion; soil moisture conservation; and weed control	no immediate effect on SOC sequestration; dependent on local climate and soil; timing of sowing is critical; germination and growing can be difficult; cost; requires personnel; water use; pests; nutrient fixation
Conservation tillage [56,57,58,59,60,61]	increase SOC; reduce erosion; soil moisture conservation; improve soil structure; fuel and time saving; improve biodiversity	the effect varies on climate, crop, and soil; SOC sequestration in deep layers is limited; weed control; pests; machinery costs; soil compaction; initial yield reduction; lack of experience
Fertilization [62,63,64,65]	increase SOC (organic); C and N supply; improve yield and biomass; indirect nutrient supply; improve soil structure and soil life (organic); long-lasting effect (organic); waste management (organic); cost (organic)	GHG emission; limited SOC sequestration (mineral); availability (organic); spoil soil structure (mineral); N-leaching, eutrophication (mineral); applicability, transport (organic); cost (mineral)
Crop rotation [66,67,68,69,70]	improve soil structure; enhance nutrient supply; increase biomass; increase SOC; reduce GHG emission; better pest and weed control; crop security;	SOC sequestration is limited, carbon loss in poorly diversified crop rotations; expertise demanding; machinery costs; profitability; contaminations
Regenerative agriculture [71,72,73]	increase SOM; improve soil structure; reduce erosion; increase soil water-holding capacity; reduce GHG emission; nutrient management; pest control; increase biodiversity	plant protection; slow return on investment (high initial costs); know-how; machinery; climate dependent efficiency; pest control can be difficult; labour intensive; legislative burdens
Agroforestry [74,75,76,77,78]	SOC sequestration; increase biomass; improve soil physical and chemical properties; improve yield; mitigate wind erosion; habitat for wildlife; mitigate GHG emission; enhance biodiversity; improve microclimate	slow return on investment (high initial costs); complex management needs; legislative burdens; pests; labour intensive

).

4.1. Cover Crops

The global use of cover crops in agricultural production has increased significantly in recent decades. Cover crops provide several benefits for both productivity and biodiversity. They serve as a primary source of carbon because both aboveground and belowground biomass remain in the field. They improve soil structure through soil aggregation processes [53,79]. Certain species (e.g., tillage radish) contribute to soil structure improvement through their loosening effect. The use of cover crops can significantly decrease uncovered soil surface during the year, which helps to reduce erosion, preserve water in soil, and control weeds [54,80]. There is a wide range of cover crop species with different roles in improving soil health. Legumes can fix atmospheric nitrogen, brassicaceous species have a role in pest control due to their glucosinolate compound [81,82], and others can enrich the soil in with carbon through their high biomass.

While some studies have failed to demonstrate a significant positive effect of cover crops on soil carbon accumulation [53,83,84], comprehensive meta-analyses highlight the clear benefits of cover crops in increasing soil carbon stocks. Bolinder et al. [85] evaluated the effect of cover crops on changes in SOC in the top 30 cm layer of soil in 20 different experiments in Europe and North America. On average, SOC increased by 9–10%, equivalent to about 330 kg of carbon enrichment per hectare each year. Results can vary widely depending on when the experiments were established. Another meta-analysis based on 28 different experiments from Europe and North America showed an average SOC enrichment of 18%. The authors emphasized that the use of cover crops for at least five years can have a significant effect on carbon stocks [55]. Hu et al. [86] also found an average SOC enrichment of 12% in their synthesis study, which evaluated data from 93 experimental sites around the world. Based on their results, significant changes can be observed after 10 years.

Globally, the use of cover crops shows a changing picture. Their use is highly dependent on local climate and soil conditions. In some parts of Brazil, for example, cover crops are used on about 30–40% of arable land, mainly because of the conversion of pasture to arable lands in recent decades and the typical monoculture production has caused rapid and significant soil degradation that requires an intensive response [87]. In 2022, cover crops were planted on 4.7% of the total cropland in the USA. According to the 2022 census, this represented a 17% increase compared to 2017 [88]. There are significant regional differences, based on soil properties, climatic conditions, and state motivation programmes [89]. While in the temperate zones of Europe and North America, the cover crops have a limited impact on the growth of the cash crops, but have sufficient effect on soil health, in the Mediterranen-type (dry and hot summer period) zones (Southern Australia and South Africa). There are limited opportunities to sow cover crops and there are no constant and evident benefits [90,91].

On average, 8% of arable land in Europe is used for cover crops, with Austria and Belgium standing out, where the share of cover crops on arable land is 29 and 21%. However, it should also be noted that a survey in 2016 found that 23% of arable land in Europe was left uncovered without cover crops or cash crops. Detailed data are presented in Figure 4 based on the 2016 Eurostat database [92].

Cover crops have not traditionally been used in Hungary, but their use has increased over the last decade [93]. The first national survey conducted in 2016 reported that cover crops were used on only 2.5% of the agricultural land. However, according to the data from the next survey in 2023, this rate exceeded 11%, indicating a more than a fourfold increase. This shift indicates that farmers are increasingly recognizing the environmental and economic benefits that cover crops offer. As Hungarian farmers seek innovative strategies to enhance their yields and promote ecological resilience, the acceptance and use of cover crops are continuing to grow. Autumn-sown crops are cultivated on 43% of arable lands, providing winter cover in these areas. After harvest, crop residues remain on 12% of the cropland for mulching. Soil cover is provided on only 3% of Hungarian arable land through the use of temporary grassland, bee pastures, green fallows, or crops sown for green manure [93]. In Hungary, cover crops are typically sown either after cereal harvest, from mid-July to the end of August, or as overwintering cover crops following autumn-harvested crops such as maize or sunflowers. While cover crops have many benefits, it is also important to consider their limitations. In Hungary, cereals are typically harvested in late June or early July. However, in recent years, the summer months have experienced several weather extremes. In both 2021 and 2022, the three summer months received at least two-thirds of the multi-year average rainfall. However, July 2022, which is a critical month for post-harvest cover crops, received only 44% of the multi-year average rainfall. Although rainfall was favourable during the summer of 2023, the average July temperature in 2024 was 3 °C warmer than the national average, and precipitation was extremely low at 30% of the multi-year average [94,95,96,97,98,99,100]. This extreme summer climate results in significant soil drying, which negatively impacts the germination and growth of any cover crop seeds sown during this time, making the success of cover crop use uncertain. Considering the weather trends outlined above, there is a high risk that cover crops sown in July will not be able to sprout and develop properly due to dry weather, so it may be worth waiting until the wetter August period before sowing. If cover crops are not sown in the summer due to climatic reasons, the soil surface remains bare from harvest until the end of August. This absence of cover increases the process of drying of soil and the risk of erosion. On the other hand, if the field is intended for autumn cereal sowing, planting cover crops in mid-August is no longer economically viable because the short growing period does not allow them to produce sufficient biomass to provide the expected agronomic benefits.

4.2. Conservation Tillage

Soil tillage techniques strongly influence soil structure and dynamics of SOC pools. Conventional plough-based tillage practices greatly impact the balance between GHG emissions and soil health by reducing the concentration of SOM and modifying soil structure. According to Al-Kaisi and Yin [101], tillage accelerates soil carbon loss by exposing SOC in inter- and intra-aggregate pores to high levels of aerobic microorganisms. These microorganisms oxidize the carbon in a process that produces CO₂. In addition, tillage also affects various physical soil properties such as aeration, water holding capacity, and temperature, which in turn play a direct role in CO₂ emission from the soil and contribute to carbon loss.

There are a number of conservation tillage systems, the main ones being no-tillage, strip-tillage, and reduced tillage. The effect of these tillage systems on carbon sequestration can vary widely under different climatic conditions, soil types, and crops [72]. A comprehensive study [58] found that while reduced tillage generally increases soil carbon content, the rate of sequestration in tropical soils can be up to five times higher than in temperate regions. In contrast, He et al. [59] conducted a meta-analysis of the effects of no-till on SOC and found that the largest increases in SOC (43.9%) occurred in areas with average annual rainfall of less than 500 mm. A smaller, but also significant (24.1%) increase in SOC content was observed in areas where the mean annual temperature exceeded 6 °C. The results confirm that the impact of soil cultivation is highly dependent on local climatic conditions.

However, the positive effect of conservation tillage practices on organic carbon accumulation is often seen only in the top layers of the soil. Ussiri and Lal [102] studied three tillage practices (conventional deep ploughing, ploughing, and no-till) after 43 years of maize monoculture in a soil tillage treatment experiment. They found that the organic matter content in the top 30 cm of the soil was significantly increased in the no-till compared to the other two tillage practices. Du et al. [60], based on a meta-analysis, also found that no-till led to an increase in organic matter content in the top 20 cm of soil, but SOC accumulation was less pronounced in the deeper layers. Haddaway et al. [61] reported a significant increase in organic carbon content in the top 15 cm of the soil layer under no-till cultivation compared to medium- and deep tillage cultivation. However, this difference was not observed in deeper soil layers. A study comparing no-tillage and ploughing also found that tillage affected soil SOC. At 0–10 cm, SOC was 15% higher in no-till than in ploughing (14.2 vs. 12.4 g kg⁻¹) treatment; at 10–20 cm, however, it was 12% higher in ploughing (12.7 vs. 11.3 g kg⁻¹). When the full depth of 0–30 cm was considered, there was no difference in SOC content, and neither the removal nor the leaving of stem residues did not affect SOC [103].

Since the 1990s, the amount of agricultural land using conservation tillage has increased worldwide. This practice is most prevalent in North and South America, as well as Australia, while it remains minimal in Europe, Asia, and Africa. In North America, 60% of arable land is managed using conservation agriculture, compared to only about 1% of arable land in Europe and about 10% globally.

In Hungary, ploughing is still the most common tillage method. However, there is a positive trend, as farmers are increasingly adopting various forms of conservation tillage practices. In 2023, approximately 1.3 million hectares were under some form of conservation tillage method, more than three times the area recorded in 2016. This means that about 34% of Hungary’s arable land is now utilizing conservation tillage practices, with the highest proportion in the South Transdanubian region (41%) and the lowest in the Northern Great Plain (27%) [104]. A 6-year-long case study from Hungary revealed that no-tillage has a positive effect on carbon sequestration compared to conventional ploughing, although annual yields were at lower levels. The non-rotary shallow cultivation method induced SOC sequestration and also resulted in beneficial yields under the investigated chernozem-type soil [105]. It is important to note that reduced tillage practices are the most widespread, while no-till practices are only applied to about 2% of arable land. Since the 2016 survey, the 24% reduction in ploughed land has been reflected in an increase in reduced tillage, as the proportion of no-till has barely increased.

4.3. Fertilization

Both animal manures and chemical fertilizers are used in crop production and compost materials are also used to improve soil quality and structure. However, their impact of these inputs on SOC is influenced by various factors such as their quality, type, and degree of humification, soil properties, and tillage practices [64]. Organic matter inputs can gradually increase the SOC content over several years [65]. The SOM content is in dynamic equilibrium influenced by mineralisation and decomposition processes. Depending on the microbial activity, the addition of fresh organic matter can stimulate mineralization, which can lead to a negative carbon balance [106]. Different types of organic and chemical fertilizers can modify the soil C cycling. Fertilizers vary significantly in their C and N content and ratios, as well as in their pH, all of which subsequently affect soil chemical and biological properties, CO₂ emissions and carbon stocks [107]. The application of organic fertilizers releases large amounts of organic C into the soil, while N fertilizers change C:N ratio of the soil [108]. In addition, the quality of the applied organic matter (e.g., lignin content or C:N ratio) significantly affects the changes in SOC stocks after fertilization [109]. Both the detectable OC content of the soil and the emissions associated with the C cycle are crucial for the assessment of soil C stocks. Following organic fertilization, emissions may increase in the short term [108], however, the effect of chemical fertilization is controversial, with examples of both increases [110] and decreases [111,112,113] in soil CO₂ emissions.

The literature suggests that the effect of fertilizer application on increasing SOC is moderate. In a study of 137 plots, it was observed that higher doses of N fertilizer promoted carbon fixation in the soil. However, C sequestration rate was lower in fine-textured soils and at higher mean temperatures [114].

A review of 20 long-term field trials across Europe shows that mineral NPK fertilization increased SOC content by 10% compared to the control [115]. Another study [116] reported an average increase of 8.5% in 64 trials. In a long-term experiment [117] examining maize–soybean biculture and maize monoculture, SOC balances were negative without N fertilizer. The application of agronomically optimal N doses resulted the SOC balance was neutral in the biculture and positive in the monoculture.

Mineral fertilization supplemented with organic fertilizers has a beneficial effect on SOC stocks. A meta-analysis reported a 4–16% increase in SOC stocks with fertilizers, and up to 9–39% when combined with organic fertilizers [118]. Another study demonstrated that applying fertilizers resulted in a 12.25% increase in SOC content, while use of organic manure led to a 32.5% increase. When both were combined, there was a 27.3% increase in SOC content [119]. In a 15-year-long experiment across three sites, the combination of NPK and organic manure (OM) increased SOC content by 11.5% [109]. Authors also showed that NPK alone also had a positive effect on SOC (increases of 7.6% and 7.8%) at two sites. Increase in SOC was significant only after the first decade, and improvements were not consistent yearly. Guo et al. [120] found that NPK positively influenced soil moisture but did not affect SOC content in a 21-year-long experiment. In contrast, following a four-year period of combined application of NPK and OM, an increase in SOC content (13.3% to 40.6%) was observed, and it was directly proportional to the amount of OM applied [121]. According to a case study from Hungary, the combination of mineral and organic fertilizer application resulted in higher SOC compared with that observed in the organic or the mineral-only treatments [122].

Composts release nutrients more slowly and have a longer lasting effect than organic fertilizers, making them more efficient at increasing SOM content [64]. The effects of biowaste compost vary widely in the literature. Emmerling et al. [123] noted a 15% increase in SOC, while Baiano and Morra [124] reported a 51.8% increase. The effectiveness of the combination of compost and N fertilizer is unclear, as results differ from study to study. For instance, in the experiment conducted by Baiano and Morra [124] and Guo et al. [125], the combination of compost and N fertilizer demonstrated lower effectiveness than compost alone. Conversely, the experiment conducted by Reimer et al. [126] reported an opposite result, where the combination of compost and N fertilizer showed greater effectiveness than compost alone. Over a 21-year period, applying 100 kg N per hectare of compost annually increased SOC by only 0.3%. When N fertilizer was added to the compost, it contributed an additional 0.1% in SOC, while the addition of N fertilizer with compost contributed an additional 0.1% increase.

A seven-year study investigated the effects of compost and half-dose compost combined with N fertilizer treatments on SOC content [127]. Both treatments significantly increased SOC levels, however, the lower dose of compost supplemented with fertilizer was more effective in increasing SOC stocks. In a 15-year study, the effect of composts with different compositions on SOC was studied [128]. The addition of municipal solid waste compost (consisting of 25% kitchen waste, 21% paper and cardboard, and 17% green waste) led to only an 8% increase in SOC, while bio-waste compost (consisting of 66% kitchen waste and 33% green waste) resulted in a significant 19% increase. Moreover, green waste–sewage sludge compost (consisting of 40% green waste, 20% sewage sludge, and 20% wood chips) showed a significant increase of 32%.

The results support the hypothesis that applying organic matter significantly increases soil nutrient composition and SOC stocks. Fertilization has been shown to increase not only yields, but also the root mass and aboveground biomass of plants. A larger proportion of the increased biomass remains on the soil surface, providing an additional source of organic matter. Consequently, from an agricultural perspective, fertilization can be considered as a strategy to enhance SOC stocks.

Since 2017, the application of solid manure in Hungary has slightly increased, rising from 4.8% of the arable land to 6.1% in 2023. However, the amount of manure applied has decreased from 18.4 t ha⁻¹ to 15.5 t ha⁻¹, indicating that the total supply of manure available for use has not increased; only the application rates have changed. Moreover, the area of land fertilized with liquid manure has increased almost by 1.5 times during this period, growing from 1.06% to 1.41%, with the current application rate of 47.9 m³ ha⁻¹ [129].

Livestock density is the number of livestock units (LU) per hectare of utilized agricultural area (UAA). The LU is a reference unit that facilitates the aggregation of livestock of different species and ages. Looking at the livestock density of the EU countries (Figure 5), it can be seen that Hungary (0.43 LU ha⁻¹ of UAA) is one of the countries with the lowest livestock density. In Hungary, the livestock density decreased moderately between 2010 and 2020, which explains the lack of a significant increase in the area of land fertilized with animal manure.

Although the positive effects of organic fertilization on SOC content are undisputed, organic fertilizers are not available in Hungary in sufficient quantities to ensure a large-scale increase in the OM content of our soils. Therefore, various climate-smart agricultural practices, such as the use of cover crops or conservation tillage, are even more valuable. It should also be noted that the combined use of different practices can have a multiplier effect and contribute to the adaptation of our soils to climate change.

4.4. Crop Rotation

As land is brought under cultivation, the carbon content of most of the soils tends to decline, leading to structural degradation. Intensive agricultural practices often involve the burning of land or the removal of crop residues, both of which eliminate opportunities to replenish SOM [69].

Crop rotation is an important component of sustainable agriculture, because it affects several soil properties. A study conducted by Zheng et al. [68] concluded the relationship between crop rotation and soil aggregates based on a comprehensive analysis of 53 experiments. They found that crop rotation improved macro-aggregate ratio by 7–14%, improved aggregate stability by 7–9%, and increased aggregate organic carbon content by 7–8% for all aggregate size ranges. Implementing a well-planned crop rotation can significantly improve degraded soil conditions. Ideally, the rotation should include more than 2–3 cash crops. Including legumes in the rotation will lead to an increase in soil N content through N fixation, leading to increased plant biomass. Over time, this can contribute to higher SOC. A properly diversified crop rotation can be expected to increase SOC by 0.15–0.5 t ha⁻¹ year⁻¹ [69,72]. The selection of crops in a rotation is a crucial factor in soil carbon sequestration. Different crops leave varying amounts and quality of plant residue in the field after harvest, which influence both soil carbon sequestration and GHG emissions. Shortening the fallow period and increasing the diversity of crops in a rotation can sometimes enhance soil carbon sequestration, but this effect is generally not as significant as that achieved through conservation tillage practices, or a combination of the cultivation technique and crop rotation. A summary study found that switching from conventional tillage to no-tillage could result in an estimated carbon sequestration of 57 ± 14 g C m⁻² year ⁻¹, whereas increasing the complexity of crop rotation could be expected to result in only 20 ± 12 g C m⁻² year⁻¹. Overall, the effect of crop rotation on carbon sequestration is much slower than the effects of tillage practices [70].

In a comprehensive study [131], a total of 127 agricultural fields were divided into 3 types of crop rotations: (1) cereals only, (2) cereals with cover crops, and (3) cereals with perennial crops. For the cereal-only rotations, the amount of carbon released to the soil was reduced by 16%, resulting in an overall reduction in SOC content of 5.3%. In contrast, both organic carbon inputs and soil SOC increased for the other two rotation types, by 42 and 6.3% for cover crops and 23 and 12.5% for perennial crops, respectively. According to a review [132], crop diversification in agroecosystems has increased soil carbon stocks globally by 3.3 to 12.5% compared to monoculture. Crop rotation can reduce soil CO₂-equivalent GHG emissions compared to monoculture, and incorporating crop residues into the soil can positively affect its OC content [133]. Wu et al. [134] studied the effect of crop rotation in wheat–potato–rapeseed–pea system, and found that the year of pea production had the highest values of soil active C, SOC, total C, nitrate-N, protein, and electrical conductivity, while the year of wheat had the lowest values. Soil respiration was maximum for pea and the lowest for rapeseed. The cultivated crop also has a strong influence on SOC stocks even in the same conservation tillage systems. A 2.75 times higher SOC content in the 0–10 cm soil layer was observed in wheat monoculture than in wheat-faba bean (Vicia Faba) intercropping system [135]. A similar finding was reported by Jagadamma et al. [136], who measured 4.7 t ha⁻¹ higher SOC content in the top 30 cm layer of a maize monoculture than in a maize–soybean rotation in a 23-year experiment [136]. Measurements in the barley monoculture also showed a higher SOC in the 0–30 cm layer than in the barley–fallow rotation, which can be explained by the higher aboveground biomass input [137].

Crop rotations in Hungary are dominated by cereals, with wheat occupying a quarter of the arable land. The total area devoted to cereals, including maize, exceeds 2.4 million hectares [138]. Such poorly diversified crop rotations result in a biologically simplified, cereal-based agroecosystem, which may also contribute to soil carbon loss [131]. A Hungarian experiment tested a crop rotation system that included winter wheat, winter rapeseed, sorghum, and winter wheat again. The results showed significant variation between the seasons and the different crops. The experiment revealed that the net CO₂ uptake was highest during the sorghum season, with 309 g C m⁻² yr⁻¹. However, the total carbon loss over a three-year period was 420 g C m⁻², indicating that carbon exported during the harvest and fallow periods exceeded the C uptake of the crops [139].

4.5. Regenerative Agriculture—A Complex Approach

Regenerative agriculture (RA), which originated in the Midwestern United States in the 1930s, is based on conservation agriculture practices. Its main principles include minimizing soil disturbance, maintaining permanent mulch, and diversifying crop rotations. These three key agricultural practices significantly increase SOM, improve soil structure, reduce erosion, and increase soil water-holding capacity [72]. RA integrates crop and livestock production to improve soil quality and reduce GHG emissions. Key practices include reduced tillage, the use of crop residues as mulch, implementing cover crops, and practicing integrated nutrient management, and pest control. It also involves complex crop rotation systems that may include woody crops and/or livestock. The main goals of regenerative agriculture are to increase SOM, improve biogeochemical cycling, and increase soil resistance to pests and diseases. By improving soil fertility through increased SOM, biological N fixation, and nutrient recycling, regenerative practices improve soil structure and increase biological activity. In addition, this approach minimizes damage from wind and water erosion by maintaining continuous soil cover [140].

RA includes many of the agricultural practices listed above, as well as the use of organic fertilizers. RA not only helps restore ecosystems (especially soils), but also increases biodiversity, protects water resources, and can mitigate climate change by sequestering carbon. By using reduced tillage practices, farmers can significantly reduce the fuel costs, and by making the right choices, fertilizer needs can also be reduced. In addition, environmental and climate protection, improved crop quality, sustainability, and various aspects of human health are becoming increasingly important, while profit from production will remain the primary concern of farmers [73].

Li et al. [141] investigated the effect of no-till and no-till combined with crop residues on soil microbial biomass compared to conventional ploughing. They found that soil microbial carbon content increased by 25% with no-till farming, and by 33% when no-till was combined with residues. This also shows that a combination of different climate-smart agricultural practices can have a better impact on increasing organic carbon stocks.

Currently, 12.5% of agricultural land worldwide is used for RA, compared to only 5% in Europe [72]. In Eastern Central Europe, soil degradation, soil compaction, and overuse of herbicides are common problems associated with intensive farming. In these countries, RA is primarily organic farming, although the two concepts are not synonymous. It is essential to promote RA and to disseminate the agroecological approach, which focuses on maintaining high productivity with minimal external inputs.

As part of the REGINA project in Hungary [142], a survey was conducted among 269 farmers. In terms of techniques already used, ‘Increase plant biodiversity’ was the most commonly chosen answer (156 respondents). ‘Reduce or eliminate mechanical interference with soil’ was used by a large number of farmers (126 respondents), but it was also the technique about which most farmers lacked knowledge (47 respondents). Among the advantages of RA, farmers mainly mentioned improved soil conditions and yield security, reduced use of fertilizers, and easy soil cultivation. Disadvantages included slow return on investment and plant protection problems. The need for continuous training, learning, and development was also expressed by farmers.

The successful adaptation and effective application of regenerative agriculture in Hungary is largely supported by the Soil Renewal Farmers Association (TMG). Through its extensive network of partners, it is a key player in the transfer of knowledge among farmers.

The Research Institute of Organic Agriculture (ÖMKI) is working on the possible development of a new national system of conditions and a voluntary certification mark for “regenerative organic farming”.

4.6. Agroforestry

Agroforestry (AF) is a land management system that deliberately integrates trees with crops or livestock on the same land. Although AF has a long tradition in many regions of the world, it has only been the focus of scientific research for the past 25 years [143]. In recent decades, AF has gained global recognition as an integrated approach to sustainable land use that provides both production and environmental benefits. Integrating trees into agricultural production systems can increase biodiversity, a pillar of sustainability [75]. The potential of AF is that, as an integrated system, it is more efficient in the use of resources (nutrients, water, and light) than monocultures and therefore has a greater C sequestration capacity, as tree crops can sequester C in their biomass over the long term [76,77]. Large amounts of biomass are released to the soil surface through the fallen canopy and pruning residues, contributing to the improvement of the soil’s physical and chemical properties.

There are a number of AF practices, the most important of which are hedgerow/alley cropping systems and shelterbelts/windbreaks. Hedgerows and alley cropping are AF practices in which trees or shrubs are planted in rows alongside crops. During the growing season, the trees are pruned, and the cuttings are used as mulch or green manure to enrich the soil and provide nutrients, especially nitrogen, to the crops. Modern hedgerow systems are designed to allow mechanized harvesting of crops by maintaining low tree densities and widely spaced rows, while providing additional sources of income such as fruits, nuts, or timber [144]. The use of different types of hedgerows can result in increased OC storage and, in some cases, proportionally higher aboveground biomass than in arable fields or even grasslands. Some studies suggest that the rate of OC storage may even be comparable to that observed in forests, and may therefore be an effective method of mitigating carbon loss from agriculture [145,146]. Axe et al. [147] found that hedgerows were significant carbon sequestrators, both in shoot and root biomass. The study found that root biomass stored an average of 38.2 ± 3.7 t C ha⁻¹, which is equivalent to 11.5 t C km⁻¹ of hedgerow. It is important to note that soil was not included in this study.

In sloping areas, the presence of hedgerows has been shown to have a dual effect, it increases SOC stocks, and provides protection against erosion, while reducing surface runoff [78]. In a five-year study, Homebegowda et al. [148] investigated the effects of two types of hedgerows on millet cultivation in fields with slopes of 5 and 10%. The results indicated that surface runoff decreased by 17–29%, soil loss was reduced by 27–48%, and SOC loss due to erosion was reduced by 42–50%, depending on the treatment. In addition, the study found that average soil moisture levels increased due to the effect of hedgerows in reducing surface runoff. As a result, millet yield exhibited a 20–33% increase as a consequence of the hedgerow intervention. The effect of hedgerows on changes in SOC stocks was studied at 25 sites within a mixed cropping and grazing system, specifically at distances of 1, 2, 3, and 10 m from the hedgerow. On average, SOC increased by 15% within 3 m of the hedgerow; however, significant variability was observed depending on the specific study site. The greatest increase in SOC was observed when there was a 1 m wide permanent grass strip adjacent to the hedge. Furthermore, greater increases in SOC near the hedgerow were found in soils with a naturally high C:N ratio, indicating a strong local effect [149].

Trees planted on the edge of agricultural land fulfil several functions. Primarily, they serve to mitigate wind erosion by either catching or slowing the wind. They also have the potential to provide additional economic benefits, such as through the cultivation of tree crops, and habitat for wildlife, thereby increasing biodiversity in the surrounding area. In areas where forest strips are present, an increase in crop yields can be expected due to the altered microclimate and improved soil properties [150].

It is estimated that AF is already practiced on about 15.4 million hectares in the EU, representing 3.6% of the total land area and 8.8% of the utilized agricultural area [151]. Kay et al. [152] estimated that 8.9% of the total arable land in the 27 EU Member States is suitable for AF practices and could potentially store between 1.4 and 43.4% of total European agricultural GHG emissions. In Hungary, ways to mitigate agricultural damages caused by climate change include the introduction of diverse, self-protecting, and seminatural crops, such as AF [153]. The key agroforestry practices in Hungary are shelterbelts and windbreaks, with an area of 16,415 hectares [154]. Honfy et al. [155] studied black locust and triticale in alley cropping in Hungary. They showed that these crops performed better with wider row spacing (>9 m). They point out that it is up to the farmer to decide what the main purpose of the alley cropping system should be (crop production, wood or biomass production, increasing biodiversity, soil conservation, etc.) and to design the rows and pruning accordingly. Király et al. [156] estimated the annual carbon sequestration of Hungarian windbreaks. They found that the carbon sequestration in the aboveground biomass of windbreaks was −2.4 t CO₂ ha⁻¹ year⁻¹ in the period 2010–2020. This corresponds to a carbon sequestration of −33.1 kt CO₂ year⁻¹, which is 0.67% of the total annual carbon sequestration of Hungarian forests. In another study, Király et al. [157] modelled the effect of doubling the extent of windbreaks on C sequestration potential. They found that the new windbreak plantations would have a significant mitigation potential, sequestering 913 kt C by 2050, corresponding to an average annual mitigation potential of 144 kt CO₂ eq.

5. Challenges and Possible Solutions

5.1. Economic Aspects

The application of CSA practices faces many economic, technical, environmental, social, and cultural challenges and constraints worldwide that need to be addressed [158]. Profitability under no-tillage, reduced tillage, or cover crops depends on the type of the production system and the main crop [159], and could be greatly reduced by adverse agroclimatic conditions (e.g., drought stress or nutrient deficiencies), when cover crops compete for soil resources [160]. Without financial compensation for yield losses, e.g., from governments or international organizations, farmers tend to reject the new or abandon the existing CSA practice [161]. Moreover, CSA often requires costly and extensive herbicide use, especially in the initial period, which leads to severe soil and water contamination and invasion by resistant weeds, threatening human health and ecosystem [72]. One possible solution would be to genetically engineer crops for integrated pest and disease management (IPM), but interpretations of CSA have traditionally rejected the use of genetically modified organisms (GMOs) [73,162].

The lower N availability resulting from the elimination or greatly reduced application of mineral fertilizers in compliance with the principles of CSA often also leads to lower crop productivity and yield, resulting in economic losses. Although organic fertilizers such as manure can increase SOM and thus crop yield, their use has been reported to increase GHG (CO₂ and N₂O) emissions, offsetting carbon and climate change benefits [163]. SOM has relatively stable elemental ratios with an average C:N ratio of 12. If more carbon is sequestered by the soil without additional N supply (i.e., mineral fertilizers), the excess carbon will be emitted to the atmosphere as CO₂. This phenomenon, with its underlying stoichiometric constraints, is conventionally referred to as the “nitrogen dilemma” [164]. The nitrogen dilemma is widely regarded as a major obstacle to the feasibility of the “4 per 1000” (4p1000.org) initiative, which aims at a yearly 0.4% increase in SOC stocks of agricultural soils. International policies, such as the EU-27’s Nitrates Directive, are focused on reducing inputs of mineral fertilizers and nitrogen leaching in order to increase organic farming and improve environmental quality [165]. Straightforward solutions to this problem include the microbially catalyzed protein production, the establishment of circular nitrogen management system, and the production of nitrogenase-based organic nitrogen using the nitrogen fixation ability of autotrophic cyanobacteria [166]. Nitrogen-fixing legume cover crops are also a promising alternative to improve soil fertility and its use is subsidized in the EU by the voluntary schemes of Common Agricultural Policy (CAP) 2023–2027, but excessive herbicide application is required to terminate their cultivation and control weed populations; otherwise, they may compete with subsequent arable crops for soil water and nutrients [167]. Furthermore, the benefits of symbiotic N fixation in terms of soil fertility are only realized in the long term, and other nutrients lost by the harvested crop should be compensated [162]. Crop residue retention is a useful strategy for both ensuring soil cover and improving soil fertility, but farmers often use residues for livestock feed or biofuel production [168].

Although crop diversification through varied crop rotations is a basic principle of conservation agriculture, local topographic, climatic, and soil conditions often limit the cultivation of many crops in a given region [169], especially if cultivation is accompanied by reduced tillage intensity, which leads to soil compaction and surface crusting [170]. Furthermore, farmers need to consider actual market opportunities when selecting crops for profitable production. Integrated crop-livestock systems, i.e., mixed farming, also bring financial losses due to the absence of arable crop yields in the ley-pasture phase of the rotation, so that compensatory crops are needed [171]. Similarly, the application of permaculture is less productive, considering that perennial grains have lower yields than annuals [172].

An important technical constraint to the wider adoption of CSA is the limited availability and high purchase cost of suitable machinery for direct sowing (especially for small-seeded crops) or for managing cover crops, especially for small farms. The use of heavy machinery and/or reduced tillage intensity frequently causes soil compaction, degradation of soil structure, risk of waterlogging, reduced seed germination, and root penetration into deeper soil layers [161].

Many social and cultural factors hinder the adoption of one or more CSA principles. Farmers often explain their reluctance by the lack of knowledge about the agroecosystems, the limited access to suitable technologies and machinery, or low competence in reduced tillage, rotation techniques, and multiple or intercropping systems [72]. Especially in the case of small farms, family structure, labour situation, traditions, and prejudices, are other important barriers to the transformation of conventional farming into conservation agriculture.

In contrast, a questionnaire survey revealed some non-financial motivations of Central European farmers to undertake CSA practice, including the concern for the natural environment and global climate, improved food quality, and interest for children and future generations [73].

In fact, there are many contradictory results and conclusions regarding the agro-environmental and economic benefits of using CSA instead of maintaining conventional practices, including SOC sequestration and climate change mitigation. This is undoubtedly discouraging for both policy makers and farmers, and is attributed to several possible reasons. The soil health benefits of adopting and applying CSA principles are often realized only 5–10 years after implementation, and are highly dependent on a variety of local circumstances, which calls for regional-scale, long-term monitoring programmes [55,173]. In addition, basic criteria for successful long-term studies need to be considered to avoid artefacts, such as sufficient number of sampling points, appropriate selection of control treatments, and the examination of at least 60 cm soil profile [174]. These monitoring studies could provide empirical evidence on the benefits and profitability of conservation agriculture [175]. Dissemination of information, adequate training, and introduction of new tools and methodologies could help farmers in decision-making and contribute to improved confidence and wider acceptance of CSA.

5.2. Policy and Regulation Aspects

The main types of instruments for environmental policy makers are: direct command-and-control regulations (EU regulations), economic instruments (taxes and subsidies), information-based instruments (labelling and certification), co- and self-regulatory mechanisms (voluntary), support, and capacity building (research and knowledge transfer) [176]. While there are many instruments in these categories, policy makers prefer a command-and-control approach where they want to ensure results, and other instruments are used only in lower risk situations [177].

The main legislation that provides the framework for agriculture in Europe is the CAP. One of the general objectives of the current CAP 2023–2027 [178] is to strengthen environmental protection, biodiversity, and climate action. Member States (MS) should design their CAP Strategic Plans (CAP-SPs) for the period 2023–2027 in a flexible way, adapted to local conditions, while contributing to the environmental goals of the farm-to-fork strategy, biodiversity strategy, and Green Deal, but their global economic and environmental benefits are questionable [179,180].

Three of the ten specific objectives (SOs) of the CAP 2023–2027 are related to the environment, namely climate change action (SO₄), sustainable development and environmental care (SO₅), and preservation of landscapes and biodiversity (SO₆). In their study, Münch et al. [181] calculated and visualized the number of interventions contributing to the SOs as defined by the MS. Their analysis revealed heterogeneity among MS, indicating that MS are able to allocate funds and interventions to their specific needs. Within the EU-27, the 28 CAP-SPs exhibited contributions ranging from 6–52% to SO_4-6. Hungary’s contributions are medium, at 25–27–32% to SO₄, −5, and −6, respectively. Notably, these values represent the highest figures among the 10 Hungarian SOs, underscoring the strategic focus of the Hungarian CAP-SP on SO_4-5-6. The Hungarian SP targets climate change mitigation, including the reduction of greenhouse gas emissions from agricultural practices, as well as the preservation of existing carbon pools and the enhancement of carbon sequestration.

Based on the indicator for SO₄, which is carbon storage in soils and biomass, the share of Utilized Agricultural Area (UAA) under supported commitments to reduce emissions or to maintain or increase carbon storage was calculated. The calculation also took into account N₂O and CH₄ emission reductions on a hectare basis. The EU average is 35.08% with different targets, ranging from a maximum of 92% for Luxembourg to a minimum of 6% for Malta. Hungary’s target is below the EU average, with a share of 21.1% [182]. Based on the result indicators, 11 MSs have higher climate ambition than the remaining 16, including Hungary [181].

The most significant innovation of the CAP is the introduction of the concept of “eco-schemes” [178]. Eco-schemes reward farmers for their role in conserving natural resources and public goods by providing support to farmers who apply production methods that go beyond the mandatory minimum requirements and contribute to the achievement of EU environmental and climate policy objectives. CAP-SPs are only a framework for achieving climate-related targets, and are only effective if farmers adopt eco-schemes [181]. In addition, a criticism of the concept of CAP by Bartkowski et al. [183] is that the European farmers are not a homogeneous group, but the CAP includes few instruments that can reflect their differences.

5.3. Human Aspects

Farmers’ decisions to adopt and participate in CSA are influenced by a variety of factors. These include their relationship with the environment, their education level, the structure of their farm, the technology and management practices available to them, the socio-economic environment, and characteristics of the policy design [184]. Acceptance of CSA may be influenced by perceptions of climate risk [185]. In Hungary, the environmental awareness of farmers is also shaped by the presence of environmentally sensitive areas on their farms and their views on environmental problems. Furthermore, the size of the farm, the education level of the farmers, the availability of farm advisory services, the farmers’ personality, and their attitudes are also factors to be considered [186,187]. The social network, which facilitates knowledge transfer, is the primary factor influencing farmers’ perceptions and adaptive capacity to environmental challenges in Hungary. Adaptive capacity varies by region depending on the degree of networking [188]. The main barriers to the use of CSA tools are lack of funding and lack of skilled labour [189]. On the other hand, due to a lack of practical knowledge on how to use innovation tools or how to analyze the data collected, farmers are only partially exploiting the potential of innovation and digitalisation [187,189]. This may be one of the reasons why, according to the European Innovation Scoreboard, Hungary is a moderate innovator with a performance below the EU average, ranked 26th, with a declining environmental sustainability and a sharp decline in the development of environment-related technologies (EC, 2024) [190].

The innovation gap has been well known for years to Hungarian policy makers. To enhance agricultural innovation, Hungary’s Digital Agricultural Strategy provides a regulatory framework for development. This strategy consists of three key pillars: (1) tools to support production processes, (2) tools to support farm-level management and decision-making, and (3) tools to facilitate product pathway integration. In this framework, a number of initiatives have been launched, including the Digital Agricultural Academy, the development of model farms, the enlargement of digital competences of farmers, the advance of advisory services, and the improvement of higher education in agriculture. A particularly important measure is the modernization and expansion of the agro-meteorological measurement network, which will provide valuable decision support for farmers. In addition, Hungary hosts various technology platforms that promote technological change and support best practices. Government subsidies connected with investments supported under the CAP further strengthen these efforts. Moreover, the European Innovation Partnership (EIP) projects and demonstration farm programmes significantly raise awareness among farmers.

Recognizing the enormous potential of networking and knowledge transfer, the CAP requires MSs to design and operate an Agricultural Knowledge Sharing and Innovation System (AKIS) to establish relationships between relevant stakeholders, including farmers, farm advisors, researchers, educational institutions, innovators, and policy makers, in order to improve the efficiency, sustainability, and competitiveness of agriculture. Our experience shows that the direct link between research and innovation and stakeholders is very important, and farmers are very inquisitive and open to active participation in demonstration events. The Hungarian AKIS is a diverse network involving ministries, advisory bodies, educational and research institutions, NGOs, media, and EU networks. The Hungarian Chamber of Agriculture (NAK) plays a central role in representing farmers’ interests and disseminating information. The National Advisory Centre coordinates advisory services, which are crucial for implementing innovations in the sector. Hungary’s CAP Strategic Plan emphasizes modernizing agriculture and forestry through innovation, knowledge transfer, and digitization. The priorities of Hungarian AKIS include strengthening links between research and practice, assessing farmers’ needs through the advisors, promoting interactive innovation initiatives, supporting intergenerational renewal, enhancing digital skills, and better utilizing the educational and research network for effective knowledge transfer [191].

6. Conclusions

The organic carbon stocks in Hungarian agricultural areas have decreased over the past decades. The SOC content of soils varies due to the genetic soil properties and the degree of degradation. Our evaluation, based on the SIMS data and the SOC: clay ratio method, indicates that the soils are excessively degraded. However, this result does not reflect the real state of the soils. Consequently, these thresholds are not applicable to Hungarian soils and specific national thresholds need to be developed for local conditions.

Agricultural practices have a significant impact on soil carbon stock. Cooperating with climate change mitigation goals, improve agricultural production and food security; the climate-smart agricultural practices can increase the SOC content of soils. According to our literature review, some prospective CSA practice could be relevant in Hungary but there are also limitations.

Due to the climatic conditions, the area of summer crops is not expected to increase in the near future. Therefore, soil cover can be ensured by crop residues, which can also provide organic matter. Although the proportion of winter cover crops could be increased, cereals sown in autumn provide soil cover over a large percentage of agricultural area.

The Hungarian Statistical Office regularly collects data only for the 12 main crops (wheat, maize, barley, rye, oats, triticale, sunflower, rapeseed, soybean, sugar beet, silage maize, and alfalfa hay). This makes it difficult to monitor the presence and proportion of new plant species in the cultivation system for the sake of diversification.

The distribution of conservation agriculture would require more subsidies than are currently available in Hungary, because of the different machinery requirements. Regenerative agriculture needs an integrated approach and farm management that incorporates livestock farming. In Hungary, there are far fewer mixed farms than farms producing only crops, so the regenerative approaches do not always include organic fertilization, which has a positive effect on soil structure.

Farming practices are always adapted to local climatic, soil, and economic conditions. The soil cover of Hungary is heterogeneous, both light and heavy textured soils are present. Farmers select the agro-techniques they use in order to maximize profit and ensure crop safety.

Achieving climate-neutral targets is not feasible with conventional farming practices. In addition, the impacts of climate change mean that these methods do not ensure secure crop production. A growing number of farmers recognize the need to adapt to climate change to maintain long-term sustainability in crop production and economic viability. They are increasingly using sensors, collecting their own data, and making decisions based on that information. Taking action to mitigate climate change is a critical next step. Widespread use of innovative agricultural technologies is essential for the development of climate-smart agriculture. Solutions such as sensors, robotic drones, precision farming, the IoT, Agriculture 4.0, and artificial intelligence, are already available. However, their adoption is often hindered by a lack of financial resources, expertise, and trust. The key to achieving results lies in the extent to which new technologies are adopted and disseminated. Direct and close collaboration among farmers, researchers, innovators, and policymakers involved in agricultural production is crucial for sharing knowledge, training, raising awareness (through living labs and digital learning platforms), and demonstrating good practices. The implementation of climate-neutral practices—such as reduced tillage, regenerative agriculture, appropriate fertilization, crop rotation, cover crops, and agroforestry—requires commitment from farmers. Environmental commitment can be increased through awareness-raising and training, but it will not override economic considerations. It is also important to address local challenges with tailored responses. For this, a supportive policy environment is essential.