Deficit Buffering Indices for Climate-Resilient Potato Water Management in Finland under CMIP6 SSPs

This study develops and applies a deficit‑based approach to estimate the minimum buffering of water deficits (summer drought) required so that potatoes in Finland avoid specified levels of water shortage under two future CMIP6 scenarios of SSP2‑4.5 and SSP5‑8.5. Using an ensemble‑based daily water‑balance model, future changes in precipitation and crop evapotranspiration are translated into spatially explicit indices of deficit severity, duration of consecutive deficit days, and the associated deficit buffering needed to keep water stress within chosen tolerance levels. The results indicate an increasing mismatch between water supply and crop water demand under high‑emission conditions, leading to more frequent and persistent dry spells and a strong rise in required deficit buffering, particularly in southern agricultural regions. In contrast, the intermediate‑emission pathway produces more moderate increases and a more limited spatial expansion of high-risk areas. Increasing the tolerated length of consecutive deficit days reduces the average deficit buffering needed but increases relative spatial variability, highlighting a trade‑off between acceptable crop stress and the scale of buffering measures. Overall, the deficit‑based indices provide a practical framework to support adaptive decision-making across Finland for climate‑resilient planning of irrigation, soil‑water management, and on‑farm buffering strategies for potatoes and other water‑sensitive crops in northern European agriculture.