Model-based assessment of climate change impacts on wheat yield under different crop management practices in the southeastern Oromia highlands, Ethiopia

Climate change presents a significant threat to wheat production in the tropical highlands of southeastern Oromia, Ethiopia. The DSSAT-CERES-Wheat model was calibrated using three years (2023–2025) of field observations at Kulumsa and independently validated using observations from Bore and Sinana. Future simulations used four CORDEX-Africa climate-model combinations under SSP2-4.5 and SSP5-8.5 for the near-future (2037–2068) and far-future (2069–2100) periods. A randomized block design tested 24 combinations of sowing date, nitrogen rate, and cultivar. Simulations showed consistent yield declines under SSP2-4.5 and SSP5-8.5 , with smaller reductions in the near future and sharper losses under SSP5-8.5 far future. Early planting consistently reduced yield losses by 15–25% relative to normal planting and 25–40% relative to late planting. Nitrogen application improved yields, though with diminishing returns; 69–92 kg N ha⁻¹ maintained near-baseline yields under SSP2-4.5 , while benefits above 69 kg N ha⁻¹ were limited under SSP5-8.5. Varietal differences showed that Shaki outperformed Boru, showing higher baseline yields and smaller climate-induced reductions. Economic analysis indicated that early planting with 69–92 kg N ha⁻¹ for Shaki maximized profitability , with gross margins exceeding 258,000 ETB ha⁻¹ under SSP2-4.5 near future. Risk-averse farmers may prefer 69 kg N ha⁻¹ due to the small marginal gain from 92 kg N. No single practice fully offset losses under SSP5-8.5 , highlighting the need for integrated strategies combining early planting, optimized nitrogen, and resilient cultivars. Location-specific optimization remains essential , and decision-support tools such as DSSAT can guide targeted adaptation. Overall, while climate change will reduce wheat yields, strategic management can substantially buffer impacts , though high-emission futures require urgent climate action and robust adaptation planning.