| 24 Mar 2026
Knowledge gaps, research strategies and robust assessment methods for soil organic carbon storage in coffee production systems
Abstract. Regenerative agriculture is increasingly promoted in the coffee sector as a strategy to enhance soil health and contribute to climate change mitigation through soil organic carbon (SOC) storage. However, robust evidence on the magnitude and drivers of SOC change in coffee production systems remains fragmented and methodologically inconsistent. We systematically reviewed 80 peer-reviewed studies assessing SOC stocks in coffee systems across major producing regions. Our analysis shows that the literature is dominated by synchronic (space-for-time) approaches (~91 %), while true diachronic studies quantifying SOC stock change over time are rare. Only a minority of studies accounted for soil bulk density differences using equivalent soil mass (ESM) approaches, fewer than half sampled below 30 cm soil depth, and more than half did not report previous land use, an essential determinant of SOC trajectories.
Across studies, SOC stocks were generally higher in coffee systems than in annual cropping systems and lower than in natural forests, with agroforestry systems sometimes approaching forest SOC levels. However, reported management effects were highly context-dependent and often confounded by differences in soil type, climate, and land-use history. As a result, current evidence does not allow robust quantification of carbon removal potential in coffee systems, nor reliable attribution of SOC differences to specific management practices.
Based on this synthesis, we provide methodological guidance for rigorous SOC research in coffee systems, including recommendations on study design, sampling depth, bulk density correction, laboratory procedures, and reporting standards. We argue that future studies must explicitly define research objectives, baseline trajectories, and the spatial scale and context to which their findings apply and distinguish between SOC stock differences and true sequestration rates. Strengthening experimental designs, harmonizing methodologies, and improving data transparency are essential to generate credible, policy-relevant evidence on SOC storage and climate mitigation in coffee landscapes.
Competing interests: At least one of the (co-)authors is a member of the editorial board of SOIL.
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Dear Editors and Authors,
This manuscript focuses on soil organic carbon (SOC) storage in coffee production systems and aims to identify knowledge gaps, evaluate methodological limitations, establish best practices, and propose a research roadmap for robust SOC assessment in global coffee‑growing regions. This work provides a systematic review of 80 studies, a comprehensive methodological assessment, and actionable guidance for SOC monitoring in coffee systems, representing an important contribution to the field. The core contribution of the manuscript is not that coffee systems are uniquely complex, but that SOC methods in coffee research are highly fragmented, inconsistent, and non‑comparable, creating an urgent need for standardized protocols. This is a valuable and timely contribution that can strongly support future research, monitoring, and policy applications.
However, the manuscript currently overemphasizes the particular complexity of coffee systems, which weakens its logical rigor and scientific credibility. Major revisions should be done before acceptance.
1. The paper contains too much generic background and common-sense discussion, which makes the text redundant and verbose. Please cut down repetitive general descriptions and condense the whole manuscript appropriately. 2. It is hard to see the special features of coffee production systems compared with other perennial crops such as cocoa and orchards. The authors need to clearly summarize the unique traits of coffee in root distribution, litter input, smallholder management, terrain and microclimate, and explain why coffee needs an independent SOC assessment system. 3. Most methodological suggestions are universal guidelines, not tailored to coffee’s actual planting conditions and field heterogeneity. More targeted operational recommendations for coffee farms should be added. 4. The manuscript only gives qualitative comparisons of SOC stocks, without quantitative summary of SOC ranges under different coffee management modes. I suggest that relevant quantitative synthesis needs to be supplemented. 5. Many cited studies confuse SOC stock difference with real carbon sequestration (net sequestration). The authors should clarify this conceptual confusion throughout the text. 6. Some paragraphs are too wordy; please simplify sentence structure and unify table, figure and reference formats.