Abstract
Widespread adoption of improved cropland management measures is advocated to increase soil organic carbon (SOC) levels, thereby improving soil fertility and mitigating climate change. However, spatially explicit insight on management impacts is limited, which is crucial for region‐specific and climate‐smart practices. To overcome these limitations, we combined global meta‐analytical results on improved management practices on SOC sequestration with spatially explicit data on current management practices and potential areas for the adoption of these measures. We included (a) fertilization practices, i.e., use of organic fertilizer compared to inorganic fertilizer or no fertilizer, (b) soil tillage practices, i.e., no‐tillage relative to high or intermediate intensity tillage, and (c) crop management practices, i.e., use of cover crops and enhanced crop residue incorporation. We show that the estimated global C sequestration potential varies between 0.44 and 0.68 Gt C yr−1, assuming maximum complementarity among all measures taken. A more realistic estimate, not assuming maximum complementarity, is from 0.28 to 0.43 Gt C yr−1, being on the lower end of the current range of 0.1–2 Gt C yr−1 found in the literature. One reason for the lower estimate is the limited availability of manure that has not yet been recycled. Another reason is the limited area for the adoption of improved measures, considering their current application and application limitations. We found large regional differences in carbon sequestration potential due to differences in yield gaps, SOC levels, and current practices applied. The highest potential is found in regions with low crop production, low initial SOC levels, and in regions where livestock manure and crop residues are only partially recycled. Supporting previous findings, we highlight that to encourage both soil fertility and SOC sequestration, it is best to focus on agricultural soils with large yield gaps and/or where SOC values are below levels that may limit crop production.
Highlights
Agricultural soils are under considerable threat due to unsustainable cultivation practices
The importance of soil organic carbon (SOC) sequestration in arable soils on climate change mitigation and food security has been recognized at the COP 21 in France in 2015, where the “4 per mille Soils for Food Security and Climate” initiative was launched by the French Ministry of Agriculture
Based on our integrative analysis of global meta-studies on soil organic carbon (SOC), we found that the overall impacts of improved cropland management range on an average from 0.2 to 0.6
Summary
Agricultural soils are under considerable threat due to unsustainable cultivation practices. Minasny et al (2017) evaluated sequestration potentials for a range of management impacts in 20 world regions and found a global sequestration potential of 2–3 Gt C yr−1 in the top 1 m of the soil profile Their estimates were criticized by de Vries (2018) due to the inclusion of around 5000 Mha of non- managed arable land and grassland, where there is a lack of nutrients such as N and P to sequester the carbon. Considering the above-mentioned limitations, Amelung et al (2020) stressed that the 4p1000 initiative is an aspirational goal due to its dependency on land use, soil, and climatic regions, and inspirational since opportunities for climate change mitigation may go hand in hand with improvements in soil health and food production security They proposed the establishment of a soil information system to assess SOC sequestration potentials, with a focus on regions where nutrient management would enhance both crop production and SOC
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