Projecting the impacts of climate change on soybean production and water requirements using AquaCrop model

Soybean production under rainfed conditions is vulnerable to climate uncertainties, particularly in semi-arid and semi-humid regions. This study assessed the impacts of climate change (SSP1–2.6, SSP2–4.5, SSP5–8.5) on soybean production and water requirements in the near (2041–2060), mid (2061–2080) and far (2081–2100) future. Simulations were conducted in specific locations in Italy (Castelfranco and Cesa) and Slovenia (Ljubljana) under rainfed and irrigated conditions, considering different thresholds of readily available water (RAW) depletion (25–100 %) to start irrigation. The results showed predominantly negative impacts of climate change under rainfed conditions. Under SSP1–2.6 and SSP2–4.5, irrigation mitigated these negative effects, leading to improved soybean performance in Italy in the near and mid future. In contrast, the mitigating potential of irrigation in Ljubljana was reduced, affecting negatively the soybean performance even under irrigated conditions. Nevertheless, the yield potential of Ljubljana remains higher compared to Castelfranco and Cesa. Soybean water productivity (WPET) followed similar trend as yield, showing minimal change except under SSP5–8.5 in the mid and far future. Climate change reduced the soybean crop water requirement (CWR) which decreased progressively from SSP1–2.6 to SSP5–8.5 across all time periods. The net irrigation requirement (NIR) was highest under SSP5–8.5, increasing from near to far future but remained stable under SSP1–2.6 and SSP2–4.5. Increasing the RAW depletion threshold for irrigation reduced soybean NIR but significantly decreased yield. Therefore, the results suggest that irrigating soybean at 50 % RAW depletion could be a viable adaptation strategy to climate change, effectively balancing the trade-offs between NIR and yield.