Cropland intensification mediates the radiative balance of greenhouse gas emissions and soil carbon sequestration in maize systems of sub‐Saharan Africa

Abstract

Sub-Saharan Africa (SSA) must undertake proper cropland intensification for higher crop yields while minimizing climate impacts. Unfortunately, no studies have simultaneously quantified greenhouse gas (GHG; CO 2 , CH 4 , and N 2 O) emissions and soil organic carbon (SOC) change in SSA croplands, leaving it a blind spot in the accounting of global warming potential (GWP). Here, based on 2-year field monitoring of soil emissions of CO 2 , CH 4 , and N 2 O, as well as SOC changes in two contrasting soil types (sandy vs. clayey), we provided the first, full accounting of GWP for maize systems in response to cropland intensifications (increasing nitrogen rates and in combination with crop residue return) in SSA. To corroborate our field observations on SOC change (i.e., 2-year, a short duration), we implemented a process-oriented model parameterized with field data to simulate SOC dynamic over time. We further tested the generality of our findings by including a literature synthesis of SOC change across maize-based systems in SSA. We found that nitrogen application reduced SOC loss, likely through increased biomass yield and consequently belowground carbon allocation. Residue return switched the direction of SOC change from loss to gain; such a benefit (SOC sequestration) was not compromised by CH 4 emissions (negligible) nor outweighed by the amplified N 2 O emissions, and contributed to negative net GWP.Overall, we show encouraging results that, combining residue and fertilizer-nitrogen input allowed for sequestering 82-284 kg of CO 2 -eq per Mg of maize grain produced across two soils. All analyses pointed to an advantage of sandy over clayey soils in achieving higher SOC sequestration targets, and thus call for a re-evaluation on the potential of sandy soils in SOC sequestration across SSA croplands. Our findings carry important implications for developing viable intensification practices for SSA croplands in mitigating climate change while securing food production.

The Impact of the Industrialized Nation's CO2 Emissions on Climate Change in Sub-Saharan Africa: Case Studies from South Africa, Nigeria and the DR Congo

“…Other things being equal, intensive farming might mediate the radiative balance between greenhouse gas emissions and soil carbon sequestration, e.g. in the controversial maize cropping systems of SSA (Zheng et al, 2023). Nevertheless, intensive farming remains the primary driver of the leaching of soil and the collapse in biodiversity.…”

“…Such a benefit (SOC sequestration) was not compromised by negligible CH4 emissions nor outweighed by the amplified N2O emissions. Overall, it contributed to negative net global warming potential (GWP) (Zheng et al, 2023).…”