Agricultural Sciences: Techniques and Innovations Vol. 10

Global freshwater resources are increasingly constrained by population growth, climate change, and competing demands from agricultural, industrial, and domestic sectors. Agriculture accounts for approximately 70 per cent of global freshwater withdrawals, with irrigated horticulture being particularly water-intensive due to the high value and water requirements of fruit, vegetable, and ornamental crops. This review comprehensively examines the physiological foundations, technological implementations, and agronomic outcomes of water-use efficiency enhancement strategies and deficit irrigation technologies in horticultural production systems. This review was conducted using secondary sources derived from existing academic literature, including peer-reviewed journal articles. The principal deficit irrigation methodologies discussed include regulated deficit irrigation, partial root-zone drying, and subsurface drip irrigation, alongside their physiological mechanisms centred on abscisic acid-mediated root-to-shoot signalling pathways that regulate stomatal conductance and plant water relations. The review synthesises evidence from diverse horticultural crops including grapevines, citrus, olive, apple, tomato, and various vegetable species, demonstrating that strategic water deficits of 20 to 30 per cent can enhance water productivity by 10 to 30 per cent whilst maintaining or improving fruit quality parameters. Emerging smart irrigation technologies integrating Internet of Things sensors, machine learning algorithms, and precision irrigation scheduling are evaluated for their potential to optimise deficit irrigation implementation. The review identifies critical research gaps including the need for crop-specific and cultivar-specific deficit irrigation protocols, improved understanding of long-term cumulative effects on perennial crops, and enhanced integration of physiological monitoring with automated irrigation systems. The findings provide evidence-based recommendations for sustainable horticultural water management strategies that balance productivity, quality, and resource conservation objectives under conditions of increasing water scarcity.