Modelling SOC dynamics on cropland under different regenerative agriculture practices and climate change scenario using RothC model in the Abbay basin of Ethiopia

Climate change remains a pressing global challenge, demanding sustainable solutions to reduce its impact. Sustainable soil management (SSM) through regenerative agriculture offers a promising pathway by enhancing soil carbon sequestration, improving fertility, and sustaining ecosystem services. However, questions persist on investment requirements, achievable sequestration rates, and spatial distribution of benefits. Outcomes are further shaped by future climate conditions. This study quantifies soil organic carbon (SOC) sequestration under SSM across four carbon input levels and two climate scenarios. Using the RothC model, SOC stock changes were simulated for croplands in Ethiopia's Abbay Basin from 2020 to 2070. Four scenarios, i.e. business-as-usual (BAU), low input (SSM1 = 20 %), medium input (SSM2 = 30 %), and high input (SSM3 = 50 %), were assessed under current and projected climates. Results show that all SSM scenarios increase SOC under current climate, though gains decline under future high-emission scenarios. SSM3 yields the largest SOC gains but faces adoption barriers from residue competition, labor, and manure availability. Carbon credit schemes and climate finance could enable wider adoption of SSM3 by offsetting costs and rewarding sequestration outcomes. Without such incentives, SSM1 and SSM2 offer more realistic entry points for smallholders but provide limited additional benefits under future conditions relative to BAU. SOC potential is spatially variable, emphasizing the need for targeted investments that balance the higher gains of intensive systems with the feasibility of lower-input options. This study highlights actionable soil stewardship measures and guides policymakers toward integrating soil carbon management into Ethiopia's soil health, climate adaptation, and food security strategies.