Sustainable Agricultural Land Management (SALM) Methodology: Modelling of Soil Organic Carbon as a Climate Change Mitigation/Adaptation Tool for Sustainable Agriculture

Two key extreme events associated with Climate Change in tropical Africa are droughts and floods. Droughts are caused by a prolonged period of low or no rainfall, leading to a shortage of water to support plants' growth and development. Floods usually attend periods of heavy downpour which force water to flow over its normal channels. Both extreme events disrupt crop cultivation and predictably lead to poor harvests in rainfed agriculture. The resultant effects are increased hunger and poverty. These can however be addressed through climate-smart agriculture (CSA). CSA is a climate resilient practice that promotes green agri-food systems. Agroforestry is one of the integrated approaches of CSA and the Sustainable Agricultural Land Management (SALM) methodology is a form of agroforestry. It minimizes drought and reduces floods on farms while at the same time promoting carbon storage in soil and plants thereby increasing crop yield. The SALM methodology calculates soil organic stock changes in a project by using soil and farm data to parameterize Roth-C to model the actual (ex-post) GHG emissions and removals from soil organic carbon (SOC) and tree biomass of the farms. The SALM project was adopted by a group of smallholder farmers in Moniya, Ibadan in 2019, and after assessing the changes in farm-based GHG emissions and removals over 3 years, the modeled soil carbon stock changes increased significantly as a result of the adoption of SALM practices from around 0:4 tCO2 ha-1yr-1 in 2019 to 3:3 ha-1 yr-1 in 2022. The average annual benefit from soil carbon sequestration is 0:8 tCO2 ha-1, the overall average mitigation benefit is 4.7 tCO2 ha-1 yr-1, and the total average GHG emission and removal profile on the farms reduced from 10.1 tCO2 ha-1 yr-1 in 2019 to 3.3 tCO2 ha-1 yr-1in 2022. There is a direct relationship between the crop yield and residues produced; the soil carbon stock changes if the residues are added to the soil as organic matter (mulch or compost). The crop yield increase is reflected by higher organic input factors and higher modelled SOC changes.