A meta-analysis of soil organic carbon dynamics under climate-smart agricultural systems in the Amazonian region

Climate-smart agriculture (CSA) systems have been promoted as a nature-based solution to ameliorate carbon losses from cropland by increasing soil organic carbon (SOC) stocks. The scale to which CSA systems [i.e., integrated cropping (iC), integrated crop-livestock (iCL) and integrated crop-livestock-forest (iCLF)] can contribute to reversing SOC losses and promote C-storage is limited in knowledge. We used a meta-analysis to give a regional-level appraisal of SOC stock changes in relation to the adoption of CSA systems in Rondônia State, Brazil. The CSA systems (iC, iCL, and iCLF) accumulated SOC at mean rates of 0.37, 0.52, and 0.76 Mg C ha −1 yr −1 , respectively, which showed that iCLF had the highest SOC change rate, study span notwithstanding. On average, the rate of SOC (Mg C ha −1 yr −1 ) change for short-term studies (< 11 years), 11–20 years, and above 20 years were 0.47, 0.93, and 0.55, respectively. Climate, altitude, and soil depth also have significant effects on the rates of SOC stock change. Oxisols and Ultisols promoted C sequestration, while Alfisols and other soil groups did not. The results from our meta-analysis established that CSA under the prevailing soil and environmental conditions can encourage more adoption of CSA by farmers, promote SOC accumulation, and consequently mitigate greenhouse gases (GHG) emissions, while guaranteeing food security. The study might support Brazil's Low-Carbon Agriculture Plan and help the country in achieving its Nationally Determined Contributions commitments on climate change mitigation through agriculture.