Water saving benefits of autumn-sown sugar beet as a climate adaptation strategy for Iran

Climate change poses significant challenges for sugar beet cultivation in Iran, where this industrial crop accounts for over 50 % of national sugar production but relies heavily on scarce water resources. This study evaluated the potential of autumn sowing as an adaptation strategy compared to conventional spring sowing under baseline (1980–2010) and future climate projections (2040–2070, RCP4.5 and RCP8.5) across 21 diverse agricultural locations in Iran. The SUCROS crop growth model was modified to simulate sugar beet response to frost damage and applied to assess yields under full and supplementary irrigation regimes. Results showed that spring-sown sugar beet failed under all supplementary irrigation scenarios, requiring full irrigation for feasibility. Autumn-sown sugar beet yields averaged 23.25 t ha−1 under supplementary irrigation compared to 89.85 t ha−1 under full irrigation at baseline. Climate change projections indicated autumn-sown yields would increase by 21.87 % (RCP4.5) and 27.80 % (RCP8.5) compared to baseline, with significant spatial variability across locations. Frost events during autumn-sown growing seasons declined substantially under future scenarios (63 % fewer in RCP4.5 and 76 % fewer in RCP8.5), with frost intensity decreasing by 4.21 % on average. Southern regions exhibited no frost events, while northeastern locations experienced the most severe frost damage. Supplementary irrigation at mid-growth stage produced the highest autumn-sown yields across most locations. These findings demonstrate that autumn sowing offers a practical adaptation strategy for sugar beet cultivation in Iran under climate change, with reduced frost risk and improved water use efficiency, particularly in warmer regions and under supplementary irrigation regimes.