Abstract
‘No-till’ (NT) agriculture, which eliminates nearly all physical disturbance of the soil surface on croplands, has been widely promoted as a means of soil organic carbon (SOC) sequestration with the potential to mitigate climate change. Here we provide the first global estimates of the SOC sequestration potential of NT adoption using a global land surface model (LSM). We use an LSM to simulate losses of SOC due to intensive tillage (IT) over the historical time period (1850–2014), followed by future simulations (2015–2100) assessing the SOC sequestration potential of adopting NT globally. Historical losses due to simulated IT practices ranged from 6.8 to 16.8 Gt C, or roughly 5%–13% of the 133 Gt C of global cumulative SOC losses attributable to agriculture reported elsewhere. Cumulative SOC sequestration in NT simulations over the entire 21st century was equivalent to approximately one year of current fossil fuel emissions and ranged between 6.6 and 14.4 Gt C (0.08–0.17 Gt C yr−1). Modeled increases in SOC sequestration under NT were concentrated in cool, humid temperate regions, with minimal SOC gains in the tropics. These results indicate that the global potential for SOC sequestration from NT adoption may be more limited than reported in some studies and promoted by policymakers. Our incorporation of tillage practices into an LSM is a major step toward integration of soil tillage as a management practice into LSMs and associated Earth system models. Future work should focus on improving process-understanding of tillage practices and their integration into LSMs, as well as resolving modeled versus observed estimates of SOC sequestration from NT adoption, particularly in the tropics.
Highlights
Agricultural practices that increase soil organic carbon (SOC) storage have been widely researched as a means of offsetting greenhouse gas emissions while improving soil health and food security (Smith et al 2008, Stockmann et al 2013, Palm et al 2014, Lipper et al 2018, Ogle et al 2019)
Historical impact of intensive tillage practices on soil carbon Implementation of IT over the historical time period in our simulations resulted in cumulative carbon losses between 6.8 and 16.8 Gt C (25.0–61.7 Gt CO2e) more than the control simulation
There has been virtually no quantification from field studies of the proportion of SOC losses attributable to tillage alone compared to other agricultural management practices following land use change (LUC) to crops, as IT is usually confounded with other management practices in such studies (Chatskikh et al 2009)
Summary
Agricultural practices that increase soil organic carbon (SOC) storage have been widely researched as a means of offsetting greenhouse gas emissions while improving soil health and food security (Smith et al 2008, Stockmann et al 2013, Palm et al 2014, Lipper et al 2018, Ogle et al 2019). Attempts at estimating global SOC gains from NT have been hindered by uncertainty in the magnitude of gains under NT from plot-scale field studies, which show widely varying capacity of NT to increase SOC depending on experimental design and geographic context (Angers and Eriksen-Hamel 2008, Luo et al 2010, Stockmann et al 2013). Despite this uncertainty, NT agriculture continues to be endorsed as an effective climate change mitigation measure by some studies and among policymakers (Lal et al 2004, Smith et al 2008, Smith et al 2014, Soussana et al 2017, Baveye et al 2018)
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