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Policymakers and businesses in Southeast Asia are increasingly interested in using carbon markets to encourage adoption of regenerative agriculture practices by farmers. These practices are thought to mitigate climate change by reducing soil carbon loss and enhancing soil carbon sequestration. However, there is uncertainty in the ability of regenerative agriculture practices to increase soil organic carbon (SOC) stocks of croplands. We reviewed 92 empirical studies that investigated the effects of 17 regenerative farming practices across 11 broad categories of crops on SOC stock or content in Southeast Asia. Our synthesis found supporting evidence for the use of organic amendments like biochar, compost, and manure, as well as cover cropping, crop rotation, and conservation tillage to increase SOC. However, studies for practices like addition of compost and manure reported increases in greenhouse gas emissions like methane (CH 4) and nitrous oxide (N 2 O), demonstrating that increases in SOC may be offset by increases in greenhouse gas emissions. Only a few studies measured both the changes in SOC stocks and greenhouse gas emissions and none of the studies completed full greenhouse gas inventories. Estimating the net impact of SOC gains and increase of greenhouse gas emissions will be necessary to understand the overall effect of practices like compost, manure and crop residue incorporation on net atmospheric greenhouse gas concentrations. If these practices are implemented for soil carbon projects, practitioners should anticipate increases in greenhouse gas emissions from soils and implement additional practices, such as alternate wetting and drying, to optimize the climate change mitigation effects of regenerative agriculture. We encourage future research on practices, such as agroforestry and changes in crop residue management, where there are few studies and little variation in experimental design and environmental conditions. Given the interest in scaling up regenerative agriculture through voluntary carbon markets to boost SOC stocks in croplands, policymakers and businesses can support research in this area by making field-collected data from their projects accessible to researchers to further the study of the impact of these practices across different abiotic conditions and soil managements. This data sharing would alleviate the paucity and improve the quality of empirical data on regenerative agricultural practices in Southeast Asian croplands, facilitate practice-specific meta-analyses, and help to optimize climate change mitigation effects of regenerative agriculture. • Regenerative agriculture practices can increase soil carbon in Southeast Asia. • These practices can also increase cropland greenhouse gas emissions like methane. • More empirical data is needed to quantify the practices' effects on soil carbon [ABSTRACT FROM AUTHOR]

Abstract: Soil C sequestration in cropland could play an important role in mitigating the rapidly increasing CO2 emissions in China. Many efforts had been dedicated to estimating the potential for C sequestration in croplands. Potential increases in SOC in China''s croplands had been recently evaluated using inventory-up-scaling simulation and crop-soil C process-based modeling. In this study, data of SOC change at monitoring sites from croplands across mainland China were collected from publications available from 1985 to 2006 to perform a statistical analysis. The data set comprises 1081 observations (404 from rice paddies, RPs and 677 from dry croplands, DCs). Frequency analysis indicates that over 70% of observations show an increase in SOC, which is higher among RPs than DCs. To quantify SOC dynamics, a Relative Annual Change Index in gkg−1 year−1 (RAC, gkg−1 year−1) is defined and calculated using the initial and final SOC values for the duration of monitored observations. RAC values ranged from −0.806 to 0.963gkg−1 year−1 for DCs and from −0.597 to 0.959gkg−1 year−1 for RPs, respectively. From this data, the average is estimated to be 0.056±0.200gkg−1 year−1 for DCs, and 0.110±0.244gkg−1 year−1 for RPs, with an overall estimate for China''s croplands, with RPs and DCs combined, of 0.076±0.219gkg−1 year−1. A mean increase in topsoil C (0–20cm) stock of China''s croplands was estimated to be 25.5TgCyear−1 (8TgCyear−1 in RPs and 17.5TgCyear−1 in DCs) between 1985 and 2006, with a total topsoil C stock increase of 0.64 Pg C over the whole period. The annual stock increase may offset ∼20%, on average, of the total CO2 emissions of China for 1994. This study suggests an important role of China''s croplands, especially rice paddies, for C sequestration to mitigate climate change. [Copyright &y& Elsevier]

There has been a careless use of terminology like “climate change mitigation” and “mitigate global warming” in scientific papers on no-tillage management in agriculture. This is because it has yet to be shown unequivocally that no-tillage can lead to carbon (C) sequestration let alone climate change mitigation. I briefly summarize evidence that shows that the claims of climate change mitigation through no-tillage agriculture are highly overstated. [ABSTRACT FROM AUTHOR]