Climate extremes, including prolonged droughts and increasingly frequent heavy rainfall events, are projected to intensify, threatening the global water cycle and agricultural productivity. Deep soil water storage may contribute to buffering such extremes, yet its influence on plant productivity and water use across agroecosystems under realistic climatic variability remains insufficiently understood. Here, we monitored soil moisture dynamics and vegetation responses in a field trial in Central Germany comprising five land-use types (two croplands: conventional and organic farming; three grasslands: intensive meadow, extensive meadow, and extensive pasture) over three years that included prolonged droughts and an extreme rainfall event. Past droughts strongly affected deep soil water storage (30–110 cm), creating legacy effects that shaped subsequent soil water availability and productivity responses. Extensive grasslands showed stronger depletion of deep soil water storage than intensive grasslands and croplands, likely driven by longer transpiration periods and greater canopy interception. In parallel, water productivity (harvested aboveground biomass per unit actual evapotranspiration) increased with land-use intensity, reflecting shorter growing periods in croplands and higher mowing frequency in intensive grasslands. However, neither deep soil water storage nor higher water productivity fully compensated for prolonged water limitations, leading to yield losses under severe droughts (precipitation < 180 mm and standardized precipitation-evapotranspiration index < −1 during the growing season). Our findings indicate that deep soil water storage and water productivity represent complementary but independent factors contributing to ecosystem resistance under drought conditions, highlighting the importance of integrating deep soil water dynamics and land-use-specific management strategies into agricultural water management.