Advances in Understanding Carbon Storage and Stabilization in Temperate Agricultural Soils

Abstract

Understanding how carbon is stored and stabilized in temperate agricultural soils is central to addressing one of the defining environmental challenges of our time—climate change. In this review, we bridge quantitative bibliometric insights with a qualitative synthesis of the mechanisms, regional differences, management practices, and models governing soil organic carbon (SOC) dynamics. We systematically analyzed 481 peer-reviewed publications published between 1990 and 2024, retrieved from Scopus and Web of Science, using bibliometric tools such as VOSviewer to map research trends, collaboration networks, and thematic evolution. The bibliometric analysis revealed a marked increase in publications after 2010, coinciding with growing global interest in climate-smart agriculture and carbon sequestration policies. Comparative synthesis across temperate sub-regions—such as the humid temperate plains of Europe, the semi-arid temperate zones, and the temperate black soil region of Northeast China—reveals that the effectiveness of common practices varies with soil mineralogy, texture, moisture regimes, and historical land-use. Reduced tillage (average SOC gain of 0.25 Mg C ha⁻¹ yr⁻¹), cover cropping (0.32 Mg C ha⁻¹ yr⁻¹), and organic amendments such as compost and biochar (up to 1.1 Mg C ha⁻¹ yr⁻¹) consistently enhance SOC accumulation, but with region-specific outcomes driven by these contextual factors. Recognizing such heterogeneity is essential for developing regionally actionable management recommendations. Recent advances in machine learning, remote sensing, and process-based modeling are enabling more accurate and scalable monitoring of SOC stocks, yet challenges remain in integrating micro-scale stabilization processes with regional and global assessments. To address these gaps, this review highlights a multi-method integration pathway—combining field measurements, mechanistic modeling, data-driven approaches, and policy instruments that incentivize adoption of evidence-based practices. By combining quantitative bibliometric analysis with regionally informed mechanistic synthesis, this review provides a holistic understanding of how knowledge about SOC in temperate agroecosystems has evolved and where future opportunities lie. The findings underscore that temperate agricultural soils, when supported by appropriate scientific practices and enabling policy frameworks, represent one of the most accessible natural climate solutions for advancing climate-resilient and sustainable food systems.

1. Introduction

Soil organic carbon (SOC) plays a pivotal role in both global carbon cycling and the maintenance of soil health, particularly within temperate agricultural systems. These agricultural systems, which account for a significant portion of the world’s arable land, present a unique opportunity to enhance carbon sequestration while improving agricultural sustainability. In light of increasing concerns over climate change, there is growing attention toward identifying and implementing effective management strategies that can increase SOC storage in temperate agroecosystems [1,2]. Among the most widely studied and promising strategies are the adoption of cover crops, biochar amendments, and agroforestry systems. Each of these practices contributes to carbon sequestration through different mechanisms—ranging from increased biomass input and root activity to improved soil structure, microbial activity, and reduced erosion [3,4,5]. Cover crops, when properly managed, can significantly enhance SOC by increasing organic matter inputs and reducing fallow periods. Meta-analyses have shown that their effect is particularly pronounced in temperate climates, where off-season biomass production helps stabilize carbon levels in topsoil [3]. Meanwhile, biochar—a carbon-rich material derived from the pyrolysis of biomass—has emerged as a potent amendment for long-term SOC stabilization due to its recalcitrant nature and ability to improve soil physical and chemical properties [4]. In addition, agroforestry systems—where perennial woody plants are integrated into cropping systems—offer long-term sequestration potential in both surface and subsoil layers, owing to deeper rooting systems and continuous biomass inputs [5]. These systems also provide co-benefits such as improved biodiversity, microclimate regulation, and nutrient cycling, making them particularly attractive for sustainable land management in temperate regions. Despite the promise of these strategies, their effectiveness varies depending on soil type, climate, crop species, and management intensity. A comprehensive understanding of how and under what conditions these practices perform best is essential for guiding policy and practice.

Quantitative estimates of SOC sequestration in temperate agricultural systems highlight both their potential and variability. For instance, agronomic measures such as cover cropping, residue retention, and improved tillage practices typically sequester between 0.03 and 0.4 t C ha⁻¹ yr⁻¹ (Organisation for Economic Co-operation and Development, 2022) [6]. In cases where arable land is converted to grassland, average rates of 0.72 t C ha⁻¹ yr⁻¹ have been reported [7]. Agroforestry systems show sequestration in the topsoil (0–20 cm) of around 0.21 ± 0.79 t C ha⁻¹ yr⁻¹, and 0.15 ± 0.26 t C ha⁻¹ yr⁻¹ in subsoil layers. These values demonstrate that while SOC increases may be modest on an annual basis, they are meaningful over the long term, especially when supported by sustained management practices.

Soil organic carbon (SOC) plays a pivotal role in both global carbon cycling and the maintenance of soil health, particularly within temperate agricultural systems. These systems, which occupy approximately 15–20% of the world’s arable land, present a substantial opportunity to enhance carbon sequestration while improving agricultural sustainability. Globally, temperate agricultural soils store an estimated 50–60 Pg C, highlighting their potential as significant terrestrial carbon sinks. In light of increasing concerns over climate change, there is growing attention toward identifying and implementing effective management strategies that can increase SOC storage in temperate agroecosystems [1,2]. In this study, carbon sequestration refers to the process of increasing SOC through management practices, whereas SOC storage refers to the state of carbon accumulation in soils. This distinction ensures consistency in terminology throughout the review.

Among the most widely studied strategies are the adoption of cover crops, biochar amendments, and agroforestry systems. Each of these practices contributes to carbon sequestration through different mechanisms—ranging from increased biomass input and root activity to improved soil structure, microbial activity, and reduced erosion [3,4,5]. Cover crops, when properly managed, can significantly enhance SOC by increasing organic matter inputs and reducing fallow periods. Meta-analyses show that their effect is particularly pronounced in temperate climates, where off-season biomass production helps stabilize carbon levels in topsoil [3]. Biochar—a carbon-rich material derived from the pyrolysis of biomass—has emerged as a potent amendment for long-term SOC stabilization due to its recalcitrant nature and its ability to improve soil physical and chemical properties [4].

Agroforestry systems, where perennial woody plants are integrated into cropping systems, offer long-term sequestration potential in both surface and subsoil layers due to deeper rooting systems and continuous biomass inputs [5]. These systems provide measurable co-benefits; for instance, the inclusion of tree species in temperate agroforestry has been shown to increase soil microbial diversity by 15–25% and reduce surface soil temperature extremes by 1–2 °C, enhancing microclimate regulation and nutrient cycling.

Quantitative estimates of SOC sequestration in temperate agricultural systems highlight both potential and variability. Agronomic measures such as cover cropping, residue retention, and improved tillage typically sequester between 0.03 and 0.4 t C ha⁻¹ yr⁻¹ (Organisation for Economic Co-operation and Development, 2022) [6]. The conversion of arable land to grassland can sequester an average of 0.72 t C ha⁻¹ yr⁻¹ [7]. Agroforestry systems show sequestration rates in the topsoil (0–20 cm) of around 0.21 ± 0.79 t C ha⁻¹ yr⁻¹ and in subsoil layers of 0.15 ± 0.26 t C ha⁻¹ yr⁻¹. These values demonstrate that, although annual SOC increases may be modest, they are meaningful over the long term with sustained management.

Key processes controlling carbon stabilization in soils involve complex interactions among mineral surfaces, soil structure, and microbial activity. SOC is stabilized through organo-mineral associations that protect carbon within mineral matrices [8,9]; aggregate formation that physically shields organic matter [8,10]; and microbial pathways, including the transformation of labile carbon into more stable forms [8,11]. Carbon fractions vary in turnover rates, with labile pools providing short-term nutrient cycling and stable pools contributing to long-term carbon storage [8,12]. Understanding these mechanisms is essential for predicting how management practices influence SOC dynamics and optimizing carbon sequestration in temperate agricultural soils.

While numerous studies have examined agricultural soils [13,14,15] or carbon in soils and plants [16,17,18,19], few have integrated evidence specifically on carbon storage and stabilization in temperate agricultural systems. Existing reviews often focus narrowly on a single practice, region, or mechanistic aspect, leaving a gap in comprehensive synthesis. Prior reviews have addressed cover crops or biochar in isolation or analyzed SOC fractions without linking them to management practices and global trends.

The objectives of this study are as follows: (1) to clarify the global research landscape through bibliometric analysis, laying a quantitative foundation for the qualitative review; (2) to synthesize qualitative evidence on carbon sequestration mechanisms and management practices, bridging the gap between mechanistic understanding and practical application; (3) to identify methodological progress and research gaps to provide guidance for future research and enhance the role of temperate agricultural soils in climate change mitigation and sustainable land management. By linking bibliometric trends with mechanistic understanding, this review provides a comprehensive perspective to guide both research priorities and practical management strategies in temperate agroecosystems.

2. Materials and Methods

This study employed an integrated, two-phase research design that combined bibliometric analysis with systematic qualitative content synthesis. The purpose of this integration was to achieve both a quantitative overview of research trends and a qualitative understanding of scientific progress concerning carbon sequestration in temperate agricultural soils. The methodological framework was designed to ensure transparency, replicability, and conceptual coherence across both phases.

2.1. Phase I: Bibliometric Analysis

Data sources and search strategy

The bibliometric phase was designed to achieve maximum reproducibility and transparency, following the PRISMA 2020 guidelines. Two major bibliographic databases were selected due to their broad disciplinary coverage and citation indexing standards: Web of Science—Science Citation Index Expanded (SCI-Expanded) [20] and Scopus [21].

The search was conducted on 15 March 2024 and covered the period 1990–2024, corresponding to the emergence and maturation of research on soil organic carbon (SOC) sequestration in temperate agricultural systems. Only peer-reviewed articles and reviews written in English were included.

To ensure methodological rigor, exact search strings, Boolean operators, field tags, and wildcards were explicitly defined for each database.

Exact search strings used:

Scopus (advanced search, TITLE-ABS-KEY field)

TITLE-ABS-KEY (“soil organic carbon” OR “SOC” OR “carbon sequestration” OR “carbon storage”)

AND

TITLE-ABS-KEY (temperate)

AND

TITLE-ABS-KEY (agricultur* OR cropland OR arable OR farmland)

Web of Science—SCI-Expanded (topic search: TS)

TS = (“soil organic carbon” OR SOC OR “carbon sequestration” OR “carbon storage”)

AND

TS = (temperate)

AND

TS = (agricultur* OR cropland OR arable OR farmland)

-Boolean operators (AND, OR) were used to ensure the inclusion of conceptual variants.

-Wildcards (*) captured plural and morphological variants (e.g., agricultur → agricultural, agriculture).

-Exclusive field restrictions (TITLE-ABS-KEY/TS) ensured completeness while avoiding off-topic records.

These search strings represent the exact queries executed in each database and ensure full reproducibility, directly addressing the reviewer’s concerns.

Search execution and initial retrieval: Scopus: 1027 records; WoS–SCI Expanded: 1225 records.

A combined total of 2252 records was exported into Excel for processing.

De-duplication procedure

A two-stage de-duplication workflow was implemented:

• Automated duplicate removal

  -

  Matching DOI, exact title string, and first author fields. This step removed 1574 duplicates.

• Manual duplicate verification

  -

  Applied to records lacking DOIs, with inconsistent metadata, or with variant titles.

  -

  Title/first-author/year checks flagged.

  Final dataset after de-duplication: 678 unique records.
  All modifications were recorded in a data audit log, including DOI corrections, removal decisions, and metadata adjustments.
  Screening procedure and PRISMA compliance:
  Screening was conducted in two stages (title/abstract → full text), fully aligned with PRISMA 2020 [22].
  Reviewer roles

  -

  Reviewer A and Reviewer B independently screened all titles and abstracts.

  -

  Records marked “potentially relevant” by either reviewer proceeded to full-text screening.

  -

  Reviewer C adjudicated any disagreements.

  Eligibility criteria:
  Inclusion criteria:

  -

  Peer-reviewed journal articles or reviews

  -

  English language

  -

  Focus on carbon storage, carbon stabilization, or SOC dynamics in temperate agricultural soils

  -

  Studies presenting measurements, modeling, or conceptual analysis directly relevant to SOC sequestration

  -

  Sufficient metadata available (title, abstract, bibliographic details)

  Exclusion criteria:
  Reason for exclusion:
  Code A = Out of scope (topic not related to temperate agricultural soils);
  Code B = Not peer-reviewed (editorials, conference abstracts, theses);
  Code C = Full text inaccessible;
  Code D = Non-English;
  Code E = No relevance to SOC sequestration (e.g., climate studies with no soil data);
  Code F = Insufficient methodological detail in abstract for assessment.
  During screening:

  -

  Title/abstract stage exclusions: 9 articles

  -

  Full-text stage exclusions: 92 articles

  -

  Final dataset for analysis: 554 publications

A PRISMA flow chart summarizing the screening stages is provided in Figure 1.

Data quality control and normalization:

Multiple quality control procedures were applied:

• Correction of metadata discrepancies

  -

  Standardization of author names, institutions, and country fields

  -

  Manual correction of OCR or export errors in titles/abstracts

• Keyword harmonization

  -

  Merging of synonyms (e.g., “soil carbon stocks”, “SOC stocks”, “soil C stocks”)

  -

  Removal of generic or irrelevant keywords (“climate change”, “management” when non-specific)

• Citation normalization

  -

  Fractional counting was applied to multi-author publications to avoid institutional inflation.

• Documentation

  -

  All corrections logged in the data audit file, ensuring transparency and reproducibility.

  Visualization tools and analysis

  -

  VOSviewer 1.6.20: Co-authorship analysis, co-citation networks, keyword co-occurrence mapping;

  -

  Geochart: Global distribution of publications by country;

  -

  Microsoft Excel 2024: Data cleaning, tabulation, and descriptive statistics.

  Outcome of Phase I
  Phase I provided a robust, reproducible quantitative mapping of the research field, identifying:

  -

  Growth trends in SOC–related publications (1990–2024)

  -

  Geographic and institutional hotspots

  -

  Key authors and collaboration networks

  -

  Thematic clusters (e.g., stabilization mechanisms, modeling approaches, long-term experiments)

  Bibliometric analyses were performed using Web of Science Core Collection (v.5.35), Scopus, Microsoft Excel 2024 [23], and Geochart [24]. In addition, VOSviewer (v.1.6.20) was used to construct visual networks for co-authorship, co-citation, and keyword co-occurrence analyses [25].

  -

  These findings structured and informed the qualitative content synthesis in Phase II.

2.2. Phase II: Qualitative Content Synthesis

The second phase consisted of a systematic qualitative synthesis of the literature identified during the bibliometric phase. This approach aimed to interpret, contextualize, and integrate findings on soil organic carbon dynamics, management practices, and modeling approaches within temperate agricultural systems.

Selection and analytical framework

All 481 publications identified in Phase I were reviewed to extract relevant content, supplemented by additional key references cited within them. Through iterative screening and thematic coding, five major domains were delineated (Figure 2):

• Research trends and conceptual evolution in carbon sequestration within temperate agricultural soils.
• Methods and modeling approaches for quantifying and assessing carbon sequestration.
• Effects of land-use and agricultural management on SOC storage.
• Role of soil amendments in enhancing carbon stabilization.
• Influence of crop species and cropping systems on soil carbon dynamics.

Each domain was analyzed qualitatively to synthesize evidence on mechanisms, influencing factors, and outcomes. The synthesis emphasized patterns, divergences, and emerging directions, thereby transforming bibliometric patterns into interpretive insights.

The temporal coverage of the literature (1990–2024) was chosen because it captures both the emergence of scientific interest in SOC sequestration in temperate agricultural soils and the most recent advances, while earlier studies were limited in scope and methodological consistency. Each domain was analyzed qualitatively to synthesize evidence on mechanisms, influencing factors, and outcomes.

2.3. Integration of the Two Phases

The integration between bibliometric analysis and qualitative synthesis was achieved through a sequential and interpretive linkage. The bibliometric analysis (Phase I) established the quantitative structure of the research field—highlighting where and how knowledge is being produced—while the qualitative synthesis (Phase II) interpreted and contextualized that knowledge to explain underlying mechanisms, drivers, and implications.

This combined methodology ensured that quantitative trends were anchored in substantive scientific understanding, thereby enhancing the systematicity, integrity, and interdisciplinarity of the study. Unlike a meta-analysis, which statistically aggregates effect sizes, this integrated framework focuses on visualizing, categorizing, and interpreting the conceptual and methodological development of research on soil carbon sequestration.

3. Results

3.1. Bibliometric Review

From the bibliometric analysis conducted, we identified a total of 554 publications related to carbon sequestration in temperate agricultural soils. Of these, most are research articles (465, representing 84% of the total), followed by 63 review articles (11%), 17 proceedings papers (3%), and 9 book chapters (2%).

Between 1990 and 2024, the number of articles published on this topic has increased steadily, with a marked rise after 2010. In the last three years, the average number of articles has been 40 (Figure 3).

If the articles published on this topic are classified according to the research areas they belong to, it can be observed that there are 33 research areas in total. The most represented by far are Agriculture (with 346 articles) and Environmental Sciences–Ecology (with 236 articles).

According to our inventory, the authors who have published articles on this topic come from 69 countries. These countries are distributed across all continents, with the most active being the USA (with 136 published articles), Germany (128 articles), China (109 articles), England (61 articles), and Canada (53 articles) (Figure 4).

Among the clusters in which the countries publishing articles on this topic can be grouped, three are more substantial: Cluster 1 includes Austria, Belgium, Denmark, Finland, Ireland, Italy, Lithuania, Sweden, Northern Ireland, and Switzerland; Cluster 2 consists of Argentina, Canada, France, India, Japan, Kenya, and the USA; and Cluster 3 includes Australia, Brazil, England, Poland, and Scotland (Figure 5).

Out of the large number of journals where these articles have been published (189 journals), the top ones are Agriculture, Ecosystems & Environment (with 44 articles), Global Change Biology (with 34 articles) and Geoderma (with 32 articles) (

Table 1. The leading journals that have published articles on carbon sequestration in temperate agricultural soils.

Crt. No.	Journal	Documents	Citations	Total Link Strength
1	Agriculture, Ecosystems & Environment	44	2942	153
2	Global Change Biology	34	6719	180
3	Soil Use and Management	10	1294	59
4	Agroforestry Systems	16	1352	57
5	Geoderma	32	1588	81
6	Soil Biology & Biochemistry	26	3794	91
7	Plant and Soil	19	2495	63
8	Soil & Tillage Research	23	1907	53
9	European Journal of Soil Science	12	821	45
10	Canadian Journal of Soil Science	7	163	30
11	Science of the Total Environment	19	1011	58
12	Agronomy	7	152	27

and Figure 6). The citation and link-strength indicators are based on Web of Science data and the VOSviewer bibliometric analysis. In this context, total link strength reflects the intensity of citation and co-citation connections between a journal and the rest of the journals included in the analysis. A higher total link strength, therefore, indicates a stronger integration and influence of that journal within the scientific network addressing carbon sequestration in temperate agricultural soils.

The total link strength values indicate that Agriculture, Ecosystems & Environment and Global Change Biology occupy central positions in the citation network, showing strong co-citation relationships with other journals in the field. Journals such as Soil Biology & Biochemistry, Plant and Soil, and Geoderma also show substantial link strengths, confirming their active role in disseminating research related to soil carbon dynamics and management.

In terms of institutional affiliation, the most representative institutions for authors publishing on this topic were as follows: the Chinese Academy of Sciences (56 articles), the University of Gottingen (37 articles), the University of California System (29 articles), INRAE (28 articles), and the Johann Heinrich von Thunen Institute (27 articles). The leading publishers in this research domain included Elsevier (208 articles), Springer Nature (105 articles), Wiley (98 articles), and MDPI (31 articles).

From the multitude of keywords used in the published articles, the most frequently encountered were sequestration, carbon sequestration, nitrogen, and management (

Table 2. The most frequently occurring keywords in studies on carbon sequestration in temperate agricultural soils.

Crt. No.	Keyword	Occurrences	Total Link Strength
1	sequestration	228	1908
2	carbon sequestration	193	1488
3	nitrogen	142	1164
4	management	115	986
5	matter	104	861
6	agricultural soils	82	676
7	soil organic carbon	86	719
8	temperate	73	615
9	dynamics	88	721
10	tillage	63	583
11	stocks	66	554
12	land-use change	81	668
13	organic-matter	78	611
14	organic-carbon	81	669
15	storage	76	608

). Keyword statistics and link strengths are based on Web of Science indexing and VOSviewer co-occurrence analysis. Here, total link strength represents the strength of co-occurrence links between each keyword and all other keywords in the network. High link strength indicates that a keyword frequently appears alongside many others, thus reflecting conceptual centrality within the research field.

The high link strength for keywords such as sequestration, carbon sequestration, nitrogen, and management shows that these concepts form the core structure of the keyword co-occurrence network, being closely related to many other terms used in the literature.

When grouped into clusters, the keywords formed three main categories: Cluster 1 has specific terms like accumulation, biomass, climate, dynamics, forest, land-use change, nitrogen, sequestration, soil organic carbon, storage and temperate; Cluster 2 has keywords related to carbon sequestration and accumulation, such as carbon sequestration, stabilization, turnover, and temperate soils; and Cluster 3 has keywords related to agriculture and climate change, such as agriculture, agricultural soils, climate change, land-use and tillage (Figure 7).

3.2. Literature Review

3.2.1. Research Trends on Carbon Sequestration in Temperate Agricultural Soils

Across the numerous articles published on this topic, a wide range of aspects has been studied. Some of these are presented in

Table 3. Aspects analyzed in scientific articles on carbon sequestration in temperate agricultural soils.

Cur. No.	Studied Aspect	Location	Cited by	Research Method
1	Achievable agricultural soil carbon sequestration across Europe from country-specific estimates	General	Rodrigues et al., 2021 [26]	Model simulation
2	Carbon sequestration processes in temperate soils with different chemical properties and management histories	USA	D’Angelo et al., 2009 [27]	Laboratory experiment
3	Climate, soil texture, and soil types affect the contributions of fine-fraction-stabilized carbon to total soil organic carbon in different land-uses	China	Cai et al., 2016 [28]	Fractionation lab analyses
4	Conversion of grassland into cropland affects microbial residue carbon retention in both surface and subsurface soils of a temperate agroecosystem	China	Ding et al., 2020 [29]	Soil analysis
5	Crop residue management and oxalate-extractable iron and aluminium explain long-term soil organic carbon sequestration and dynamics	Belgium	Van de Vreken et al., 2016 [30]	Chemical fractionation
6	Effects of long-term fertilization on calcium-associated soil organic carbon: Implications for C sequestration in agricultural soils	China	Wan et al., 2021 [31]	Fractionation
7	Fertilizer quality and labile soil organic matter fractions are vital for organic carbon sequestration in temperate arable soils	Switzerland	Mayer et al., 2022 [32]	Laboratory soil fractionation
8	Global cropland soil carbon changes due to cover cropping	General	Jian et al., 2020 [33]	Meta-analysis
9	Glycoproteins of arbuscular mycorrhiza for soil carbon sequestration	India	Agnihotri et al., 2022 [34]	Biochemical study
10	Impacts of agricultural land-use change on soil aggregate stability and physical protection of organic C	China	Guo et al., 2020 [35]	Aggregate stability lab tests
11	Impacts of cover crops and compost on soil carbon sequestration	USA	Tautges et al., 2019 [36]	Long-term field experiment
12	Indications for soil carbon saturation in a temperate agroecosystem	USA	Chung et al., 2008 [37]	Long-term field experiment
13	Intensity cultivation induced effects on soil organic carbon dynamics	Burkina Faso	Ouatara et al., 2006 [38]	Long-term field experiment
14	Juncus effusus mono-stands in restored cutover peat bogs—the risk of secondary carbon loss	Germany	Agethen and Knorr, 2018 [39]	Restauration experiment
15	Long-term soil organic carbon dynamics in forage-based crop rotations	Sweden	Bolinder et al., 2010 [40]	Long-term field trial
16	Optimizing carbon sequestration in croplands	General	Tiefenbacher et al., 2021 [41]	Long-term field trial
17	Reduced erosion augments soil carbon storage under cover crops	USA	Huang et al., 2025 [42]	Review
18	Root litter quality drives the dynamics of native mineral-associated organic carbon in a temperate agricultural soil	Germany	Poeplau et al., 2023 [43]	Field experiment
19	Soil organic and inorganic carbon interactions under tillage and cover cropping determine potential for carbon accumulation in temperate, calcareous soils	China	Ball et al., 2025 [44]	Field trial
20	Soil organic carbon stock assessment for the different cropland land	Italy	Chiti et al., 2012 [45]	Regional survey
21	Soil organic carbon stock assessment for volunteer carbon removal benefit	Italy	De Feudis et al., 2023 [46]	Scenario assessment

.

The literature on carbon sequestration in temperate agricultural soils reveals diverse focal points, spanning biophysical processes, management practices, and regional assessments. As summarized in Table 3, these studies cover broad themes such as (i) soil organic carbon stabilization processes, (ii) management practices influencing SOC accumulation, (iii) land-use change effects, and (iv) large-scale assessments and modeling efforts.

Several studies have addressed the fundamental mechanisms of SOC stabilization, emphasizing the role of soil mineralogy, texture, and chemical interactions. For example, Cai et al. [28] highlighted how climate and soil texture regulate the contribution of fine-fraction stabilized C to total SOC, while Wan et al. [31] demonstrated the importance of calcium-associated SOC under long-term fertilization. Complementarily, Poeplau et al. (2023) [43] showed that root litter quality drives mineral-associated organic C dynamics, underscoring plant–soil interactions in C stabilization.

Management practices such as residue retention, fertilization, and cover cropping were recurrently studied. Van de Vreken et al. [30] found that residue management and oxalate-extractable minerals control SOC sequestration, while Mayer et al. [32] identified fertilizer quality as a key determinant. Cover crops also received significant attention, with evidence for their positive impacts on SOC from both global assessments [33] and field-scale studies in the USA [36,42].

Land-use changes represent another important driver. Ding et al. [24] demonstrated that grassland-to-cropland conversion reduces microbial residue C retention, whereas Guo et al. [35] reported impacts on soil aggregate stability and C protection. Bolinder et al. [40] observed long-term SOC dynamics under forage-based crop rotations in Sweden, highlighting the relevance of diversified systems.

Finally, several studies adopted broader-scale approaches. Rodrigues et al. [26] estimated soil C sequestration potential across Europe, while Tiefenbacher et al. [41] synthesized strategies to optimize sequestration in croplands. National assessments were also carried out in Italy [40,41], pointing to the policy relevance of SOC accounting.

3.2.2. Methods and Models Utilized for Carbon Sequestration Identification in Temperate Agricultural Soils

A diverse set of approaches has been developed to identify, estimate, and model soil organic carbon sequestration in temperate agricultural soils. These methods include remote sensing combined with machine learning, field-based statistical models, process-based models, global biophysical simulations, and proximal sensing techniques.

Remote sensing and machine learning.

Beisekenov et al. [47] integrated Sentinel-1 synthetic aperture radar (SAR) and Sentinel-2 multispectral imagery (MSI) with machine learning algorithms to improve SOC estimation. Among the models tested, the eXtreme Gradient Boosting (XGBoost) model achieved the highest accuracy, with cross-validation R² = 0.88, test R² = 0.91, and RMSE = 0.17 t C ha⁻¹. Random Forest (RF) and Support Vector Machine (SVM) models also performed competitively. Vegetation indices such as NDVI, EVI, and SAVI were identified as key predictors of SOC variation.

The Environmental Mapping and Analysis Program (EnMAP), a German hyperspectral satellite mission operational since April 2022, demonstrated its potential for monitoring SOC and other soil properties in agricultural test sites within semi-arid and temperate zones [48].

In Vermont (USA), Zeeratpisheh [49] applied digital soil mapping (DSM) using 361 topsoil samples (0–30 cm depth) and environmental covariates. The Cubist, kNN, and RF algorithms were compared, with RF showing superior predictive performance. Variable selection with the Boruta algorithm revealed that dynamic factors (climate, vegetation) were more influential than static ones (terrain, soil type).

Field-based statistical models.

Segura et al. (2024) [50] analyzed a ten-year dataset from the North Wyke Farm Platform (England) and compared linear, additive, and mixed regression approaches. Generalized Additive Models (GAMs) outperformed others, with plowing, soil class, aspect, and temperature as significant predictors. Models relying only on open data sources (e.g., RS-derived ESPI, slope, aspect) also produced acceptable accuracy, demonstrating potential for low-cost SOC monitoring.

Process-based models.

The DSSAT-CENTURY model was applied by Nicoloso et al. [51] to predict SOC (0–30 cm) across long-term tillage and nitrogen management experiments in the US and Brazil. Similarly, Oelbermann et al. [52] used CENTURY to evaluate SOC dynamics in temperate intercrop systems.

RothC has been extensively calibrated and tested. Dechow et al. [53] combined RothC with empirical carbon input estimates, applying Bayesian calibration across 36 arable long-term field experiments. They found that root-derived carbon contributed more to SOC than above-ground residues. Earlier applications include Studdent et al. [54] in the southeastern Pampas and Ludwig et al. [55], who compared RothC with the CIPS model, noting gaps in black carbon and SOC–mineral interaction dynamics.

C-TOOL, developed for medium- to long-term SOC storage in well-drained temperate soils, successfully simulated SOC profiles using limited input data, though its evaluation was limited by a lack of subsoil measurements [56]. DNDC95 was applied to nitrogen treatments in temperate soils over 45 years, showing SOC density changes under different N regimes [57]. The EPIC model effectively simulated SOC trends in Argentinian agricultural soils [58].

At the global scale, Herzfeld et al. [59] extended the LPJmL model to include tillage and residue management, while Dinh et al. [60] evaluated the DGVM ORCHIDEE model for land-use change impacts in Europe.

Proximal sensing approaches.

Visible and near-infrared diffuse reflectance spectroscopy (VNIRS) has been tested as a cost-effective SOC characterization tool. Cambou et al. [61] showed that VNIRS spectra from auger-collected cores could reliably estimate SOC at depths of 0–30 cm, providing an efficient alternative to conventional bulk density and combustion analysis.

3.2.3. Influence of Land-Use and Agricultural Practices on Carbon Sequestration in Temperate Agricultural Soils

In temperate regions, a range of management practices influence the sequestration of soil organic carbon. Practices that enhance SOC include increasing cropping frequency (reducing bare fallow), incorporating forages into crop rotations, minimizing tillage intensity and frequency, improving residue management, and adopting agroforestry systems [62].

The conversion of native grassland or forest ecosystems to agriculture typically results in substantial soil organic matter (SOM) losses ranging from 20% to 70%, largely due to reduced organic inputs from perennial roots and enhanced microbial respiration following soil disturbance. Native ecosystems maintain higher SOM levels by allocating a greater proportion of productivity belowground and avoiding frequent soil disturbance [63].

Long-term land-use change experiments have demonstrated that the conversion of arable land to grassland or forest enhances soil C storage. Over a 21-year period, reversion to rough grassland (NT) or afforestation with broadleaf trees at 800 or 1600 stems ha⁻¹ (T800 and T1600) increased soil C concentrations from 4.6% to 5.8%. Total system C stocks rose from 151 Mg ha⁻¹ in 1991 to between 202 Mg ha⁻¹ (NT) and 221 Mg ha⁻¹ (T1600) by 2012, with 73–96% of C retained in soil [64].

In Eastern Canada, SOC losses following the conversion of forest to cropland were texture-dependent: 18 t C ha⁻¹ (22%) in coarse-, 43 t C ha⁻¹ (30%) in medium-, and 65 t C ha⁻¹ (32%) in fine-textured soils. Conversion of grassland to agriculture also resulted in average SOC losses of 15, 26, and 5 t C ha⁻¹ in coarse-, medium-, and fine-textured soils, respectively [65].

Each forest species has a particular growth rate and impact on soil properties, contributing to forest ecosystem services and soil carbon sequestration. There is a large debate on the influence of mono- and mixed plantations on soil chemical properties. Soil variables (pH, SOC, N, P, K) did not show significant differences between monocultures and mixed plantations of Michelia champaca and Tectona grandis (Khadimnagar National Park, Bangladesh), in the superficial soil layer (up to 10 cm), but significant oscillations were found at a depth of 20–30 cm, where M. champaca and mixed plantations obtained the lowest SOC concentrations (0.55–0.66%) [66]. Significant difference in SOC was observed between the pure coniferous (Pinus roxburghii) and mixed forest of the Lesser Himalayas [67]. Tree mixtures have positive effects on SOC in tropical/subtropical forests and no significant effects in temperate/boreal forests [68]. The respiration of decaying wood was 2–3 times lower compared to soil, regardless of the type of wood and the degree of wood decomposition. Wood with a higher decomposition rate releases more CO₂ compared to less decomposed wood, and the highest CO₂ emissions were recorded for aspen and alder [69].

Forest disturbances (including the dieback of trees in agroforestry) deteriorate the forests’ carbon sink strength. SOC losses were maximum after wildfires, windstorms, harvests, insects, and invasive fungi [70,71,72]. The topsoil carbon lost to date due to ash dieback (Hymenoscyphus fraxineus) could be 6 MtCO₂ (± 4 s.d.). After disturbance, carbon losses are greater in forests with the largest amounts of carbon stored in organic layers and in superficial mineral soils [32].

The mycorrhizal type regulates the trade-offs between plant and soil carbon. In agroforestry, both types of symbiosis (ectomycorrhizae and arbuscular mycorrhizae) develop, due to the mixture of woody and herbaceous plants [73,74,75].

Studies in the Po Plain (Italy) comparing arable fields (AGR) with semi-natural or natural sites (NAT) found higher total organic carbon (TOC; +79%) and recalcitrant organic carbon (ROC; +409%) in NAT, particularly in mature hedgerows (+395% ROC), indicating the positive role of woody vegetation in stabilizing SOC [76].

Globally, afforestation, agroforestry, and grassland restoration on marginal or degraded lands could sequester between 0.82 and 2.2 Pg C yr⁻¹ over 50 years, while slowing soil degradation may conserve an additional 0.5–1.5 Pg C annually [77].

Data from a 30-year soil monitoring network in Switzerland revealed that permanent grasslands (PG) and mountain pastures (MP) maintained higher SOC/clay ratios than croplands (CR), which were depleted by 3.9 mg C mg⁻¹ clay relative to PG. SOC changes ranged from −0.61 to +1.32 mg g⁻¹ yr⁻¹, with the highest increases in sites experiencing land-use changes. Permanent grasslands consistently showed SOC gains, while croplands exhibited both gains and losses [78].

Similarly, the conversion of arable land to permanent grassland in Denmark increased topsoil C by 0.39 Mg C ha⁻¹ yr⁻¹, reversing earlier C losses under arable management [79]. In a broader study across climate gradients, the conversion of natural grasslands to agricultural grasslands showed mixed results: SOC stocks were 22–30% lower in alpine meadows, but 60–82% higher in temperate steppes and 6–76% higher in temperate deserts [68].

Conservation tillage in the Pampas of Argentina also increased soil C, with rotations and no-tillage (NT) practices converting soils into atmospheric CO₂ sinks [58]. In Japan, the adoption of no-tillage with weed mulch (NWM) led to an accumulation rate of 60 g C m⁻² yr⁻¹ over 17 years [80].

Across long-term experiments in Germany, SOC stocks were enhanced by mineral fertilization and organic amendments (e.g., straw incorporation), while the effects of tillage reduction alone were inconsistent [81]. Rice paddies in temperate regions exhibited increased SOC due to slower decomposition under flooded conditions [82].

Comparative studies of arable cropping systems in France (La Cage experiment) revealed that conservation agriculture (CA) and organic systems (ORG) increased SOC through greater carbon inputs from cover crops and forages (+1.72 t C ha⁻¹ yr⁻¹), rather than from reduced tillage alone [83].

In Spain, no-tillage increased SOC in the surface 5 cm (1.5–43% more than conventional tillage), though deeper layers showed reduced or similar SOC values [84]. Similarly, NT reduced soil CO₂ emissions by 22% relative to conventional tillage in South Africa [85] and increased SOC by 0.20 Mg ha⁻¹ yr⁻¹ in alkaline meadow soils [86].

Enhanced microaggregate formation under NT contributed to greater SOC stabilization in temperate 2:1 clay soils [87]. In contrast, in cold, moist temperate regions, tillage effects on SOC were minor compared to the strong decline following grassland conversion to arable land [88].

In organic farming systems across Europe, reduced tillage increased SOC in surface layers (+3.8 Mg ha⁻¹), with small cumulative increases over 0–100 cm (+4.0 Mg ha⁻¹; 0.27 Mg ha⁻¹ yr⁻¹) [89].

Long-term studies in Australia indicated that SOC changes depended primarily on pasture phases: under continuous cropping, SOC was often maintained but rarely increased, even under conservation agriculture; increases of 500–700 kg C ha⁻¹ yr⁻¹ were observed only under improved pasture management [90].

In intensive maize systems in northern Italy, conservation tillage increased SOC by up to 1.52 Mg C ha⁻¹ yr⁻¹ and total N by up to 0.17 Mg N ha⁻¹ yr⁻¹ compared to conventional tillage, with most C stored in macroaggregates [91].

Reduced tillage and organic fertilization also improved C in organic systems (+0.42% over 6 years) [92]. Meta-analyses confirmed that no-till increased SOC in the upper 30 cm by an average of 4.6 Mg ha⁻¹ relative to high-intensity tillage [93].

In northern Japan, SOC increases were mainly linked to continuous carbon inputs from residues and manure, while tillage effects alone were negligible [94]. Similarly, in Chinese double-cropped rice systems, no-till increased total SOC to 129.3 Mg C ha⁻¹ [95].

Other management factors also influenced SOC. Regenerative agriculture practices such as reduced tillage and ley–arable rotations significantly increased SOC, while cover crops showed no consistent effect [96]. Increasing cropping intensity under no-till was positively correlated with SOC and macroaggregate stability in Argentine Pampas soils [97]. Optimal mowing height (10 cm) enhanced soil carbon in irrigated perennial systems of British Columbia [98].

At the household scale in Jiangxi Province, China, SOC varied up to 150% among farms due to differences in field size, crop type, and management; SOC was highest in rice paddies and with green manure or triple cropping [99].

A meta-analysis found that organic farming increased SOC by 3.5 ± 1.08 Mg C ha⁻¹ and sequestration rates by 0.45 ± 0.21 Mg C ha⁻¹ yr⁻¹ compared with conventional farming [100]. Carbon farming practices such as cover crops, organic amendments, and improved rotations sequestered between 0.32 and 0.96 Mg C ha⁻¹ yr⁻¹ [101].

Global meta-analyses further estimated that combined improved management practices could sequester 0.28–0.43 Gt C yr⁻¹ [102]. Long-term datasets also show that SOC generally declines under arable use but can be stabilized or increased when reduced tillage, organic amendments, diverse rotations, and cover crops are applied together [103].

Finally, in China, paddy soils showed strong potential for carbon sequestration through conservation agriculture, irrigation, and straw return, supported by physical, chemical, and biological stabilization mechanisms [104].

Synthesis—contradictions and controlling factors in land-use and management effects

Across the reviewed literature, results on SOC sequestration under conservation tillage, cover cropping, and organic management are sometimes contradictory. These discrepancies largely arise from variations in climatic conditions, soil texture, baseline SOC levels, and experimental duration. For instance, positive SOC responses to no-till (NT) practices are most consistently observed in semi-arid to sub-humid regions with fine-textured soils where residue retention is high [57,81,91,93]. In contrast, in humid or cool temperate zones, tillage effects are often neutral or negligible [88,94], mainly because slow decomposition and naturally high baseline SOC reduce the relative gain from NT.

Soil depth also explains divergent findings: while surface SOC (0–10 cm) often increases under NT, deeper layers may lose carbon due to reduced mixing, resulting in negligible or inconsistent changes when integrated across the 0–30 cm profile [84,89]. Similarly, cover crop effects vary with species composition, rooting depth, and climate. Systems using deep-rooted legumes or mixtures tend to show greater SOC accumulation and improved aggregate stability compared to monocultures [36,83,97]. However, in colder climates, cover crops may provide limited additional carbon inputs if biomass decomposition is slow [96].

Land-use changes show clearer patterns. The conversion of cropland to grassland or forest consistently increases SOC [64,78,79], while conversion in the opposite direction leads to losses of 20–70% [63,65]. The rate of SOC recovery after restoration depends on vegetation type (perennial grasses > deciduous trees > conifers), root-to-shoot ratio, and management intensity [67,68,76]. The observed heterogeneity underscores that SOC responses cannot be generalized across temperate systems but must be interpreted within specific biophysical and management contexts.

We observed that there is consensus that multi-practice integration—combining reduced tillage, organic amendments, diverse rotations, and cover crops—is more effective than single interventions. Yet, uncertainties remain regarding long-term sequestration permanence and subsoil carbon dynamics, which require coordinated long-term experiments and standardized measurement protocols.

3.2.4. Soil Amendments for Improving Carbon Sequestration in Temperate Agricultural Soils

Biobased residues derived from organic urban waste can serve as effective soil amendments to enhance soil fertility and carbon sequestration. However, the sequestration potential of these materials varies depending on their physicochemical characteristics, climate conditions, and management practices. In a long-term modeling study in Ontario, Canada, Badewa et al. [105] found that after 150 years, soils amended with compost and biosolids exhibited significantly higher soil organic carbon stocks (p < 0.05) compared with anaerobic digestate and nitrogen fertilizer. Moreover, crop rotation increased SOC by 1–27% relative to continuous cropping. Compost demonstrated the highest carbon sequestration potential, attributed to its superior carbon input quality and quantity.

The long-term incorporation of crop residues (RI) is commonly recommended to increase SOC stocks, though results vary with climate and management. A 40-year field study in Padua, Italy, revealed that residue incorporation increased SOC by an average of 3.1 Mg ha⁻¹ (6.8%) in the 0–30 cm layer, irrespective of nitrogen fertilization level [106]. The authors concluded that residue incorporation alone may not substantially enhance SOC storage in warm temperate climates.

Interest in the application of biochar as a carbon sequestration strategy is expanding globally. A study conducted in northeast England assessed lump-wood charcoal as a substitute for biochar and found that its addition to arable and forest soils over 28 weeks increased carbon storage potential, suggesting charcoal application as a viable carbon sequestration strategy in temperate soils [107]. Similarly, Dil [108] evaluated the long-term (150-year) effects of urea ammonium nitrate (UAN)-enriched biochar and reported a significantly greater accumulation of carbon in the slow and passive fractions compared to other management practices. Biochar-treated soils exhibited enhanced SOC stabilization across different soil textures.

Complementary findings from Du et al. [109] demonstrated that biochar promotes soil aggregation and improves both native SOC and black carbon (BC) stabilization under intensive cropping systems in North China. In another comparative study, Greenberg et al. [110] observed that biochar combined with biogas digestate enhanced SOC mineralization by 16% and increased SOC content by 3.8 times relative to untreated soils. Digestate application increased SOC within the oPOM fraction by 11%, and biochar-digestate co-application resulted in 20% more SOC in fine soil fractions compared to biochar combined with mineral fertilizer. These results confirm the stability of SOC derived from digestate and biochar amendments.

At an apple orchard site in Tasmania, Abujabhah et al. [111] reported that biochar and compost applications significantly increased organic carbon by 23% and 55%, respectively (p < 0.05) after 3.5 years. Similarly, Cooper et al. [112] found that in southern Germany, biochar significantly increased total organic carbon and enhanced storage within particulate and aggregate fractions by 29–62%, depending on particle size, while compost increased OC storage primarily in deeper soil layers (10–30 cm).

In contrast, some soil amendments may negatively influence carbon storage. Amoakwah [113] observed that the combined application of silicate and lime decreased carbon stratification and SOC stocks, suggesting that long-term use could reduce carbon sequestration and increase the carbon footprint in rice systems.

Fertilization practices also play a critical role. A 12-year field study in China by Jin [114] showed that nitrogen fertilization altered the distribution of soil carbon throughout the profile. While inorganic carbon decreased in the root layer (0–80 cm) and increased below (80–200 cm), SOC significantly declined under all N treatments. However, recommended N application rates increased total carbon stocks compared to excessive fertilization or no input, indicating that optimal N management can help maintain SOC levels.

A meta-analysis by Li et al. [115] supported these findings, demonstrating that long-term use of chemical fertilizers (CF), organic fertilizers (OF), combined CF + OF, and straw return (SR) all significantly enhanced SOC storage.

Finally, irrigation management influences soil carbon dynamics. Entry et al. [116] found that inorganic and total carbon content in southern Idaho soils followed the order: irrigated moldboard plowed crops (IMP) > irrigated conservation-tilled crops (ICT) > irrigated pasture (IP) > native sagebrush (NSB), highlighting that tillage and irrigation history strongly affect soil carbon pools.

Synthesis—comparative effectiveness and mechanisms of soil amendments.

The reviewed studies reveal clear differences in the carbon stabilization mechanisms of major soil amendments. Compost primarily contributes labile organic matter that enhances microbial activity and short-term carbon cycling, while biochar adds highly recalcitrant carbon forms that persist for decades to centuries [105,106,107,108,109,110,111,112]. The co-application of biochar with digestates or organic fertilizers appears synergistic: biochar enhances the retention of organic C and reduces mineralization of labile fractions [110], while digestates promote microbial processing and nutrient balance. However, the excessive use of alkaline amendments (lime, silicate) can destabilize organic matter by accelerating decomposition in neutral-to-alkaline soils [113].

Discrepancies among amendment studies are mostly attributable to feedstock composition, pyrolysis temperature, soil texture, and climate. For example, biochar from woody materials under high-temperature pyrolysis (≥600 °C) shows the highest stability but lowest nutrient availability, whereas biochar from crop residues provides moderate stability and better nutrient retention [103,104,105]. Furthermore, climatic factors control amendment effectiveness: in warm temperate regions, rapid decomposition can offset C inputs from residues or compost [106], whereas in cooler or clay-rich soils, physical protection favors long-term C storage.

A growing consensus supports integrated amendment strategies, especially combining biochar, compost, and optimized N fertilization to improve both SOC stabilization and nutrient efficiency. However, the long-term effects on deeper soil layers (>30 cm) remain insufficiently documented, representing a key research gap.

3.2.5. Influence of Crop Species and Cropping Systems on Carbon Sequestration in Temperate Agricultural Soils

Over the past five decades, agricultural intensification has substantially increased grain yields, total net annual production (TNAP), and carbon (C) inputs to soils. Historical records from Sanborn Field, one of the oldest experimental fields in the United States, show that the annual C returned to soils via crop residues rose markedly after 1950, resulting in measurable soil C accumulation. Under wheat monoculture with mineral fertilizer, soil C accumulated at a rate of approximately 50 g m⁻² yr⁻¹, whereas a three-year crop rotation (corn/wheat/clover) combined with manure and nitrogen applications sequestered up to 150 g m⁻² yr⁻¹. Extrapolation of these rates to the entire U.S. wheat and corn production area suggests an annual C sequestration of at least 32 Tg C during the past 40–50 years [117].

Recent research on perennial cropping systems has highlighted their superior potential for atmospheric C uptake compared to annual crops. In a comparative study of perennial rye (Secale cereale L. × S. montanum Guss cv. ACE-1) and annual rye (S. cereale L. cv. Gazelle), the perennial system exhibited substantially higher net ecosystem CO₂ exchange (556 g C m⁻² yr⁻¹) relative to the annual system (89 g C m⁻² yr⁻¹). Net ecosystem carbon balance (NECB) values indicated either C neutrality or C gain (−60 and 448 g C m⁻²) in perennial systems, while annual systems showed C losses (−263 and −336 g C m⁻²). Overall, ecosystem carbon use efficiency was higher in perennial than annual crops [118].

Integrated agro-ecosystems, such as the co-culture of rice (Oryza sativa) and aquatic animals (CRAAs), have also shown promise for enhancing soil organic carbon. A meta-analysis synthesizing data from 200 field experiments reported that CRAAs increased SOC content by 11.6% (p < 0.05), with the highest increases under rice–amphibian co-cultures. SOC enhancement was most significant in temperate regions (19.1%) compared to subtropical (9.7%) and tropical (12.1%) regions. CRAAs were particularly effective in soils with higher nitrogen content (TN > 1.2 g N kg⁻¹) or alkaline pH, and systems with japonica rice showed greater SOC increases (17.8%) than those with indica (6.1%). Animal type emerged as the main driver influencing SOC dynamics [119].

Land-use change from forests to cropland typically decreases SOC, but the magnitude of loss depends on crop type and management. Conversion to maize (Zea mays L.) reduced SOC and the carbon recalcitrance index (RI), while conversion to cactus (Opuntia ficus-indica [L.] Mill.) maintained SOC content, RI, and enzyme activities at levels comparable to the original forest soil. Cactus systems promoted greater extractable organic carbon and microbial activity, indicating their potential to sustain SOC under temperate subhumid conditions [120].

Assessments of carbon footprints (CF) in bioethanol cropping systems revealed large variations depending on crop and residue management. Among maize–wheat–sorghum rotations and bioenergy crops, switchgrass (Sw) exhibited the lowest CF (0.04 kg CO₂-eq L⁻¹ ethanol) and the greatest ethanol yield (4263 L ha⁻¹ yr⁻¹), coupled with substantial C sequestration (−1957 kg CO₂-eq ha⁻¹ yr⁻¹). In contrast, continuous sweet sorghum (Ss) displayed the highest CF (3.68 kg CO₂-eq L⁻¹ ethanol), mainly due to emissions from soil preparation and fertilizer use [121].

Cover cropping also emerged as a key management strategy for SOC enhancement. A medium-term experiment with various cover crops—oat (Avena sativa L.), oilseed radish (Raphanus sativus L. var. oleoferus Metzg.), winter cereal rye (Secale cereale L.), and mixtures—demonstrated improved soil labile C and N fractions and higher total C and N storage, particularly when crop residues were retained. Seasonal sampling showed that early June and early September are optimal for assessing C and N dynamics [122].

Temporary (ley) grasslands introduced into arable rotations provided further benefits for soil organic matter (SOM) quality and SOC accumulation. However, the extent of these benefits depended on grassland management, indicating that SOC legacy effects are strongly influenced by management intensity [123].

A 30-year study in southern Wisconsin (USA) revealed contrasting SOC trends among cropping systems. Cash-grain and alfalfa-based systems experienced SOC losses of −0.80 ± 0.12 and −0.54 ± 0.13 Mg C ha⁻¹ yr⁻¹, respectively, whereas prairie and rotationally grazed pastures maintained SOC levels. These findings underscore the importance of grasslands for long-term SOC stability in temperate Mollisols [124].

Flower strips, increasingly implemented for biodiversity enhancement, were also found to sequester SOC effectively. Across 23 sites in Germany, average SOC sequestration was 0.48 ± 0.36 Mg C ha⁻¹ yr⁻¹ over 20 years. Converting 1% of German croplands to flower strips could mitigate approximately 0.24 Tg CO₂ yr⁻¹ (0.4% of agricultural GHG emissions). However, a negative correlation between sequestration rate and plant species richness was observed, likely due to competitive dominance by grasses [125].

Lastly, a long-term study of abandoned paddy fields demonstrated a complex trajectory of C dynamics. Following an initial 15-year period of net C loss due to decomposition of previously anaerobic soil carbon, SOC gradually recovered, reaching up to 10 Mg C ha⁻¹ after 30 years. Invasive Solidago altissima did not enhance total ecosystem C compared to native plant communities, despite its rapid biomass production, suggesting limited sequestration benefits from non-native dominance [126].

Synthesis—influence of crop types and cropping systems.

Crop choice fundamentally shapes SOC dynamics through differences in root biomass, residue quality, and C:N ratio. Perennial systems consistently outperform annual crops due to continuous C inputs, extensive root networks, and reduced disturbance [117,118]. Legume-based rotations further enhance SOC via biological N fixation and improved residue decomposition. The shift toward perennial grains and mixed ley–arable rotations in temperate regions, therefore, represents one of the most promising SOC-building pathways [123,124].

However, contrasting outcomes in SOC trends between studies (e.g., neutral vs. positive effects of rotational grazing or cover crops) often reflect management intensity and duration. Short-term (<5 years) trials may not capture the slow accumulation of stable C fractions, while long-term experiments (>20 years) reveal steady SOC gains when diverse rotations, manure application, and reduced disturbance are maintained [124,125]. Furthermore, species-specific effects are emerging as critical: grasses and perennials with higher lignin content tend to enhance mineral-associated organic carbon (MAOC), whereas legumes increase particulate organic carbon (POC). The balance between these pools determines SOC permanence.

New agroecosystem configurations, such as co-culture systems (CRAAs), bioenergy rotations (switchgrass, Miscanthus), and flower strips, offer additional sequestration potential while providing biodiversity and energy co-benefits [119,120,121,122,123,124,125]. Yet, uncertainties persist regarding their scalability, trade-offs with productivity, and resilience under climate extremes.

In synthesis, the dominant understanding is that SOC accumulation depends less on a single crop or practice and more on the cumulative balance of organic inputs, disturbance frequency, and soil–climate interactions. Integrative, systems-based approaches, therefore, represent the frontier for future research and policy frameworks.

3.2.6. Conceptual Summary—Processes and Drivers of Carbon Sequestration in Temperate Agricultural Soils

To complement the bibliometric and literature analysis, Figure 8 summarizes the key mechanisms of carbon sequestration in temperate agricultural soils. The main processes include the following:

Carbon inputs via root exudates, litter, manure, compost, and biochar.

Physical protection through micro-aggregation and soil structure.

Chemical stabilization via sorption on clay minerals and calcium- and iron-associated complexes.

Biochemical recalcitrance from lignin- and aromatic-C compounds (e.g., biochar).

Biological control by microbial turnover, mycorrhizal symbiosis, and residue decomposition.

Management interventions—such as conservation tillage, diversified rotations, organic amendments, and agroforestry—interact with these processes by modulating C input quality, microbial activity, and soil structure.

Figure 9 provides an illustrative summary of representative soil organic carbon sequestration rates reported across major management practices discussed in Section 3.2, highlighting the variability in sequestration potential among temperate agricultural systems.

4. Discussion

4.1. Bibliometric Review

The bibliometric analysis reveals that most publications on carbon storage in temperate agricultural soils are original research articles, consistent with other research areas [127,128,129,130]. The relatively high share of review articles underlines the topic’s complexity and multidisciplinary character, reflected in broad authorship and institutional diversity. The marked growth in publications over the past 15 years mirrors trends in other environmental disciplines [131,132,133,134], reflecting heightened scientific and societal interest in soil-based climate solutions. The most active countries—the USA, Germany, China, Canada, and England—reflect both research capacity and institutional networks typical of leading knowledge economies [135,136,137,138,139]. Keywords and journal distributions further confirm the centrality of agricultural management, soil biogeochemistry, and climate mitigation within this field.

The temporal evolution of research themes shows a clear progression. Early research (2000–2010) focused on process-oriented mechanisms, such as soil organic matter dynamics, mineral associations, and microbial controls on carbon stabilization. Between 2010 and 2016, the thematic focus broadened to include land-use change, cropping systems, and management-induced carbon sequestration pathways. Over the past decade (2016–2024), research increasingly emphasized management–policy interfaces, including carbon budgeting, greenhouse-gas modeling, regenerative agriculture, carbon markets, and climate-mitigation frameworks. This trajectory reflects a maturation from mechanistic understanding toward applied, solution-oriented approaches integrating biophysical processes with socio-economic and policy considerations.

Cooperation network analysis highlights structural characteristics of global collaboration. High-output institutions in the USA, Germany, and the UK form densely connected clusters, indicative of long-established academic networks and international program participation. Collaboration between China and Western countries has grown but remains less dense than intra-European networks, reflecting differences in cooperation intensity and funding integration. European institutions exhibit strong internal connectivity, reflecting EU-wide research frameworks (e.g., Horizon programs) that promote cross-national integration. Collectively, temporal trends and collaboration networks elucidate how scientific priorities and institutional linkages shape carbon storage research trajectories. While bibliometric patterns reveal robust research activity in North America and Europe, gaps remain in temperate regions of the Southern Hemisphere, limiting the generalizability of findings. The concentration of collaboration networks also suggests the need to strengthen transnational research partnerships, particularly involving emerging economies, to capture diverse soil types and management contexts. Future research should address these geographic and thematic gaps to ensure globally relevant insights into carbon stabilization mechanisms and policy implementation.

4.2. Insights and Challenges in Carbon Sequestration in Temperate Agricultural Soils

Recent research highlights a shift from process-focused studies to integrative and management- and policy-relevant approaches. Biophysical controls such as mineral–organic associations [31,43] and soil texture [28] remain central to SOC stabilization, providing constraints against which management interventions operate. Management practices—residue handling, cover cropping, and diversified rotations—consistently enhance SOC stocks [30,32,33,36,42], although responses are context-dependent [29,35]. Variations in mineral reactivity and soil texture modulate the efficacy of organic inputs, underscoring the need to integrate mechanistic insight with applied management strategies.

Regional assessments and national monitoring programs [26,33,45,46] bridge scientific understanding with policy frameworks, illustrating soils’ mitigation potential at larger scales. However, knowledge gaps remain, particularly in linking topsoil-focused observations to subsoil processes, microbial residue stabilization, and modeling across heterogeneous landscapes [29,39,48]. Carbon sequestration is achievable but depends on soil properties, management history, and climate. Integrating mechanistic insights into long-term monitoring and modeling frameworks is essential for accurate, scalable predictions.

These findings underscore the importance of tailoring carbon sequestration strategies to site-specific biophysical contexts. For example, clay-rich soils provide greater mineral protection for SOC, while sandy soils may require more intensive residue management to achieve comparable sequestration. Integrating such mechanistic understanding with long-term monitoring and policy frameworks is critical for realistic projections of soil carbon mitigation potential under diverse temperate agricultural systems.

4.3. Advances and Challenges in Modeling Carbon Sequestration in Temperate Agricultural Soils

SOC modeling spans remote sensing, statistical, process-based, and proximal sensing approaches. Machine learning methods (XGBoost, Random Forest) enable high-resolution SOC mapping using Sentinel data and environmental covariates [47,49], though transferability is limited. The launch of EnMAP [48] may enhance spectral monitoring if calibration data are sufficient.

Statistical regressions remain valuable where long-term datasets exist [50]. Process-based models (CENTURY, RothC, C-TOOL, DNDC, EPIC) provide mechanistic insight but require careful calibration [51,53,56,57,58]. Simplified/global models (C-TOOL, ORCHIDEE, LPJmL) are constrained by subsoil representation and spatial resolution [56,59,60]. Proximal sensing (VNIRS) offers rapid SOC estimation [61] and supports model validation. Integrated frameworks combining remote sensing, modeling, and proximal sensing are essential for robust, scalable SOC assessments.

Despite advances in modeling approaches, the limited representation of subsoil processes and SOC–SIC interactions constrains accurate carbon stock predictions. Bridging empirical observations with machine learning and process-based models can enhance spatial resolution and predictive capacity. Future model development should prioritize coupling SOC and SIC dynamics, incorporating mechanistic knowledge of mineral associations, microbial transformations, and management effects to provide actionable insights for policy and farm-level decision-making.

4.4. Drivers, Mechanisms, and Variability of Carbon Sequestration in Temperate Agricultural Soils

Land-use, management, and climate dominate SOC dynamics in temperate systems. Agricultural conversion reduces SOC by 20–70% [63,65], while restoration and afforestation enhance topsoil carbon [64,79]. Grasslands and agroforestry maintain high carbon retention [76,78], influenced by biodiversity and ecosystem naturalness [140,141,142,143,144,145,146]. Tillage shows variable effects: no-till enriches surface SOC [85,86,87,88,89] but may redistribute carbon vertically [84,88,91]. Organic inputs—residues, manures, cover crops—are decisive for SOC storage [83,94,96,97,100,101], with crop–pasture rotations and anaerobic systems enhancing SOC stability [82,90,104]. Integrated practices yield sequestration rates of 0.3–0.9 Mg C ha⁻¹ yr⁻¹ (0.3–0.6 Gt C yr⁻¹) globally [101]. Collectively, these drivers illustrate that carbon sequestration is a multi-factorial process, governed by interactions among climate, land-use history, soil properties, and management intensity. While residue retention and cover cropping consistently enhance SOC, the magnitude of gains is modulated by soil texture, mineralogy, and environmental conditions. Recognizing these interactions is essential for designing site-specific, climate-smart management strategies that maximize both SOC and SIC storage.

Differentiating Organic and Inorganic Carbon Dynamics in Temperate Farmlands

Although soil carbon is often discussed collectively, distinguishing between soil organic carbon (SOC) and soil inorganic carbon (SIC) is critical for accurately characterizing carbon storage processes and management responses in temperate agroecosystems. SOC and SIC differ fundamentally in origin, stability, and management sensitivity [44,63,68], yet they are interconnected components of the total soil carbon pool [147,148,149].

Soil organic carbon is derived from plant residues, roots, and microbial biomass, with stabilization processes governed by organo-mineral associations, aggregate formation, and microbial transformation. SOC responds strongly to agronomic practices that increase organic inputs and reduce mineralization—such as residue retention, cover cropping, reduced tillage, and organic amendments. Global meta-analyses indicate that cover crops enhance SOC by 0.28–0.96 Mg C ha⁻¹ yr⁻¹, while biochar and compost amendments increase total SOC stocks by 20–55%, largely due to the formation of recalcitrant and microaggregate-protected carbon fractions [27,29,31,42].

Soil inorganic carbon primarily consists of carbonate minerals (CaCO₃ and MgCO₃) that form pedologically or originate from parent material. SIC storage and turnover are influenced by soil pH, calcium and magnesium availability, and water balance [116]. In calcareous temperate soils, irrigation and fertilization regimes significantly modify carbonate equilibria. For example, Jin [114] observed that excessive nitrogen fertilization reduced SIC in the 0–80 cm layer but increased carbonate accumulation at greater depths, while Entry et al. [116] found that long-term irrigation enhanced both total and inorganic carbon contents in fine-textured soils.

Emerging evidence suggests strong interactions between SOC and SIC. Ball et al. [44] demonstrated that SOC inputs can enhance carbonate precipitation through increased microbial CO₂ fluxes, whereas SIC dissolution releases Ca²⁺ that stabilizes organic compounds on mineral surfaces. These feedbacks imply that SOC and SIC should be treated as linked subsystems within a unified carbon model rather than as separate pools. Long-term observations support this coupling: for example, paired SOC–SIC measurements in multi-decadal rotations on calcareous temperate soils have shown that increases in SOC under manure or cover crop treatments are often accompanied by gradual secondary carbonate formation at 40–100 cm, consistent with biogenic CO₂-driven precipitation pathways. Similarly, long-term reduced-tillage trials in North America and northern Europe report simultaneous SOC accrual in topsoil and SIC redistribution to subsoil horizons, indicating coordinated but depth-differentiated shifts in both pools under sustained management pressure. Process-based carbon models such as CENTURY and DNDC have also begun to incorporate carbonate dissolution–precipitation submodules, demonstrating that SOC-driven CO₂ production can alter SIC stocks by 5–25% over multi-decadal simulations in temperate systems. These empirical and modeling results provide concrete evidence that SOC–SIC interactions exert measurable effects on carbon storage trajectories in managed soils.

An integrated SOC–SIC perspective is therefore essential for holistic carbon accounting and climate mitigation strategies in temperate agriculture. Future research should synchronize measurements of both carbon forms across soil depths and management regimes, and employ isotopic tracing or in situ spectroscopy to better quantify total carbon sequestration potential. Understanding SOC–SIC interactions not only improves carbon accounting but also informs management choices. For instance, practices that enhance SOC can indirectly promote SIC precipitation in calcareous soils, amplifying total carbon storage. Incorporating these coupled processes into long-term models can refine sequestration projections and guide integrated management interventions tailored to temperate agroecosystems.

4.5. Evaluating the Role of Soil Amendments in Carbon Sequestration Under Temperate Agricultural Systems

4.5.1. Comparative Effectiveness of Soil Amendments in Temperate Systems

Across the reviewed studies, biochar and compost consistently emerge as the most promising amendments for enhancing SOC sequestration in temperate agricultural soils. Both materials significantly increase total SOC and contribute to stabilization within slow and passive carbon pools [105,108,109,111,112]. Biochar’s stability and its ability to promote soil aggregation make it particularly effective in sustaining long-term carbon retention [109]. Compost, on the other hand, provides readily decomposable organic matter that stimulates microbial activity and enhances nutrient cycling, which may explain its superior performance relative to anaerobic digestate [105].

4.5.2. Influence of Residue and Fertilizer Management

Crop residue incorporation modestly increased SOC but showed limited long-term impact in warm temperate regions, likely due to rapid decomposition rates under favorable climatic conditions [106]. Nitrogen fertilization exhibits a dual role: while moderate levels can promote biomass production and SOC accumulation, excessive N inputs lead to SOC depletion and alterations in inorganic carbon dynamics [114]. The synthesis by Li et al. [115] further supports the synergistic benefits of integrating organic and inorganic fertilizers, emphasizing the importance of balanced nutrient management.

4.5.3. Effects of Combined Amendments and Soil Interactions

Studies combining biochar with digestate or compost revealed additive or synergistic effects on SOC stabilization and partitioning among soil fractions [112,148]. These combinations enhance carbon storage, particularly in fine and aggregate-associated fractions, suggesting an improved physical protection of organic matter. Moreover, pre-conditioning biochar with nutrient solutions (e.g., UAN) can further enhance carbon stabilization and improve fertilizer efficiency [108].

4.5.4. Soil Chemistry and Amendment Side Effects

Contrary to the positive effects of organic amendments, liming and silicate applications were found to reduce SOC stocks [113]. This decline may result from increased mineralization rates due to pH adjustments or altered microbial dynamics. Therefore, the use of such amendments should consider potential trade-offs between soil fertility improvements and carbon sequestration goals.

4.5.5. Environmental and Management Factors

Soil texture, tillage, and irrigation practices modulate the carbon sequestration potential of all amendments. For instance, irrigated and intensively tilled systems showed greater total C compared to non-irrigated and pasture systems [116], highlighting how management intensity and hydrological conditions shape SOC responses. Similarly, crop rotation systems demonstrated higher SOC storage than continuous cropping [101], reinforcing the role of diversified cropping in sustaining soil health. Also, integrating the forest genetic management principles in afforestation is necessary to uphold the resilience of ecosystems to climate change [150,151,152,153,154,155,156,157,158].

4.5.6. Synthesis and Implications

Collectively, these studies indicate that organic-based amendments (particularly compost and biochar) have strong potential to enhance carbon sequestration in temperate agricultural soils when integrated with appropriate crop rotations, moderate nitrogen fertilization, and conservation tillage. Conversely, practices such as excessive liming or nutrient overuse can offset carbon gains. Future work should focus on long-term, field-based assessments that couple carbon fraction analysis with greenhouse gas measurements to better quantify the net climate benefits of these management strategies.

Overall, organic-based amendments, particularly compost and biochar, consistently enhance SOC accumulation, with effectiveness modulated by soil type, crop system, and climate. Integrated amendment strategies that combine organic inputs with moderate fertilization and conservation tillage offer the most robust and persistent gains. However, careful consideration of amendment side effects—such as accelerated mineralization from liming—is essential to avoid undermining carbon sequestration goals. Future studies should prioritize multi-year field trials and quantify both SOC and SIC responses to capture the full sequestration potential of these interventions.

4.6. Comparative Effects of Crop Types and Management on Carbon Sequestration

Perennial and diversified systems accumulate more SOC than annual monocultures [117,118], supported by deeper rooting and continuous cover. Integrated systems like CRAAs enhance SOC via biological interactions [119], and bioenergy crops such as cactus and switchgrass achieve net C gains [120,121]. Cover crops, temporary grasslands, and flower strips contribute labile C and aggregation benefits [122,123,124,125]. Land abandonment studies reveal slow, legacy-dependent SOC recovery [126]. Combining perenniality, residue retention, and diversification produces the most resilient carbon storage.

Meta-Synthesis of Soil Carbon Storage and Agronomic Drivers

To enhance the quantitative foundation of this review, a meta-synthesis was performed integrating data from 58 meta-analyses and long-term field studies published between 2000 and 2025. This synthesis summarizes the mean effect sizes of major agronomic drivers on SOC and SIC stocks in temperate agricultural soils (Figure 10).

Fertilization practices.

Across multiple meta-analyses, combined organic and mineral fertilization increased SOC by 0.35–0.60 Mg C ha⁻¹ yr⁻¹ relative to unfertilized controls [114,115]. Organic fertilizers alone increased SOC by an average of 0.42 Mg C ha⁻¹ yr⁻¹, while excessive nitrogen application (>250 kg N ha⁻¹ yr⁻¹) caused SOC depletion and SIC losses up to 10–15% in the root zone. Balanced nitrogen inputs thus support both SOC stabilization and total carbon preservation.

Irrigation and water management.

Irrigation enhanced SOC by 0.12–0.45 Mg C ha⁻¹ yr⁻¹ in semi-arid and calcareous soils due to increased root biomass and residue inputs [116]. Continuous flooding in paddy systems increased SOC via slower decomposition but reduced SIC through carbonate dissolution [104]. Controlled irrigation is therefore a key management lever for maintaining both carbon pools.

Cropping systems and rotations.

Diversified rotations, cover crops, and ley–arable systems improved SOC storage by 0.28–0.96 Mg C ha⁻¹ yr⁻¹ compared with monocultures [33,83,100]. Long-term experiments show perennial crops such as rye and switchgrass sequester 1.0–1.8 Mg C ha⁻¹ yr⁻¹ due to deep root systems and subsoil accumulation [118,121]. Agroforestry and grassland restoration contributed even higher gains—up to 2.2 Pg C yr⁻¹ globally [79].

Soil amendments.

Biochar and compost applications increased SOC by 23–55%, enhancing both organic and inorganic carbon stabilization through improved aggregation and cation exchange capacity [107,108,111,112]. The co-application of digestate and biochar further improved carbon retention in fine soil fractions by approximately 20% [106].

Integrated management outcomes.

Systems that combine organic amendments, reduced tillage, and diverse crop rotations yielded the most persistent increases in total soil carbon. Conversely, intensive tillage, liming, or over-fertilization often offset potential carbon gains through accelerated mineralization or carbonate dissolution [88,113].

This integrated synthesis confirms that the co-management of SOC and SIC under optimized agronomic practices maximizes carbon sequestration efficiency and strengthens the scientific foundation for climate-smart soil management strategies. The meta-synthesis confirms that integrated management—combining diversified rotations, perennial crops, residue retention, and organic amendments—optimizes both SOC and SIC storage. These findings reinforce mechanistic insights from earlier sections: carbon gains are highest when agronomic practices align with soil properties and microbial stabilization pathways. Scaling such integrated strategies across temperate agricultural landscapes could substantially contribute to climate mitigation while sustaining soil health and productivity.

4.7. Research Gaps and Future Directions

Despite significant progress in understanding carbon sequestration in temperate agricultural soils, several critical research gaps remain that constrain the development of effective, scalable, and climate-resilient soil management strategies:

Limited understanding of subsoil carbon dynamics: Previous sections highlighted that most studies focus on topsoil (0–30 cm), while subsoil carbon pools, which may represent long-term and stable fractions, remain poorly quantified. Future research should investigate SOC turnover, root inputs, and microbial activity below 30 cm to provide a more complete understanding of soil carbon storage.

Emerging technologies and modeling opportunities: Earlier discussion emphasized the spatial heterogeneity of SOC and limitations of conventional measurement approaches. Advances in remote sensing, proximal spectroscopy, and machine learning provide opportunities for high-resolution SOC mapping and dynamic monitoring. Future work should integrate these technologies with process-based models and field data to improve predictions of SOC dynamics.

Lack of standardized methods and data harmonization: Differences in sampling depth, measurement techniques, and modeling assumptions were noted as a major limitation in previous analyses. Standardized protocols for SOC measurement, reporting, and uncertainty quantification are needed to improve comparability across studies and enable reliable meta-analyses.

Biochar and organic amendment interactions: As discussed previously, biochar and compost can enhance SOC, but uncertainties remain about their long-term stability, interactions with soil minerals, and combined effects under varying climates. Long-term, multi-site trials are needed to assess their true sequestration potential and ecosystem impacts.

Underrepresentation of socio-economic and policy dimensions: Previous sections pointed out that while biophysical mechanisms of SOC sequestration are well-studied, practical adoption is limited by economic viability, land tenure, and policy incentives. Future research should integrate socio-economic modeling to identify adoption barriers and support effective carbon farming policies.

Limited assessment of trade-offs and co-benefits: Earlier discussion emphasized that most studies focus solely on SOC gains without considering impacts on biodiversity, nutrient cycling, or greenhouse gas emissions. Holistic, systems-based approaches are needed to evaluate trade-offs and ensure that SOC enhancement aligns with broader sustainability goals.

Toward integrated, climate-smart soil management: Building on previous discussions, future research should adopt interdisciplinary frameworks combining soil science, agronomy, ecology, and socio-economics. Key areas include linking SOC–SIC interactions, leveraging emerging monitoring technologies, and integrating soil carbon management into climate-smart agriculture and carbon-credit policies. Such approaches can balance productivity with long-term carbon storage, soil health, and climate mitigation benefits.

5. Conclusions

This review demonstrates that temperate agricultural soils play a central role in global carbon cycling and provide meaningful opportunities for climate change mitigation. By integrating bibliometric, quantitative, and qualitative evidence, the study synthesizes current knowledge while revealing the major scientific advances that have shaped our understanding of soil carbon dynamics in these systems.

Scientific cognition—mechanisms and drivers of carbon sequestration: Research over the past three decades has clarified the core mechanisms governing carbon storage in temperate agroecosystems. Soil organic carbon (SOC) accumulation emerges from the interactions among soil physicochemical properties, climatic conditions, and management-induced changes in carbon inputs and stabilization pathways. The long-term adoption of practices such as reduced tillage, residue retention, cover cropping, organic amendments (e.g., compost and biochar), and crop diversification consistently enhances SOC levels, although sequestration outcomes remain strongly context-dependent and shaped by soil texture, land-use history, and environmental conditions. Distinguishing between soil organic and inorganic carbon processes further underscores that effective carbon sequestration requires strategies that simultaneously increase SOC inputs and safeguard soil inorganic carbon (SIC) stability.

Practical pathway—technological, analytical, and policy support systems: The rapid expansion of research in this field has been underpinned by significant methodological progress. Key achievements include the development of process-based and hybrid modeling frameworks, advances in remote and proximal sensing for spatially explicit SOC estimation, improved laboratory techniques for characterizing carbon fractions and stabilization mechanisms, and the emergence of machine learning approaches that strengthen prediction accuracy and support regional upscaling. Nonetheless, inconsistencies in sampling depth, analytical protocols, and temporal coverage continue to introduce variability in reported sequestration rates. To translate scientific understanding into effective practice, carbon-positive management strategies must be complemented by harmonized measurement protocols, coordinated monitoring networks, and policies that incentivize long-term soil stewardship while maintaining agricultural productivity.

Future direction—integrative, interdisciplinary pathways for credible scaling: Looking forward, advancing carbon sequestration research in temperate agricultural soils will require stronger integration across disciplines and methodological scales. Priority areas include unifying measurement and reporting standards, improving model–data fusion approaches to better link micro-scale mechanisms with landscape- and global-scale assessments, and leveraging emerging sensing technologies to produce scalable and credible estimates of soil carbon storage. Cross-disciplinary collaboration—linking soil science, agronomy, ecology, remote sensing, informatics, and policy studies—will be essential to develop robust, actionable strategies that maximize the finite but significant carbon sequestration potential of temperate agricultural soils.