Climate-Smart Agriculture Strategies for Improving Water-use Efficiency under Extreme Weather Conditions

Climate-smart agriculture (CSA) seeks to sustain productivity, strengthen adaptation and resilience, and, where feasible, reduce greenhouse gas emissions. Across these goals, water-use efficiency (WUE) and water productivity are central because climate change is intensifying hydroclimatic variability, increasing the frequency of hot extremes and droughts, and amplifying risks from compound heat–moisture events that can include both water deficit and moisture excess within the same growing season. This review synthesises advances since the mid-2000s in understanding and improving WUE under extreme weather, focusing on the coupling of crop physiology, soil–plant–atmosphere processes, irrigation and soil-water management, and emerging digital decision support. Evidence indicates that WUE is not a single trait but an outcome of interacting processes operating from leaf to canopy to field and basin scale, shaped by phenology, vapour pressure deficit, rooting dynamics, soil evaporation, and management that partitions limited water towards productive transpiration. Contemporary CSA strategies that improve WUE under extremes include stress-timed deficit irrigation and regulated deficit approaches, partial root-zone drying, alternate wetting and drying in rice, residue-based soil cover and conservation-agriculture principles, and improved matching of cultivar phenology to evolving risk windows. At the same time, adaptations can be maladaptive under compound extremes if designed for single hazards, highlighting the need for multi-stress resilience. Rapid progress in remote sensing of evapotranspiration, sensor networks, and artificial intelligence (AI) is enabling more timely and spatially explicit irrigation scheduling and drought response, but deployment constraints remain, including cost, data governance, skills, and infrastructure. The review concludes that the next frontier for CSA is integrated optimisation of WUE that explicitly accounts for extremes, trade-offs across scales, and equity in access to water-saving innovations.