Impact of Deficit Irrigation on Major Irrigated Crop Yield and Water Productivity: A Meta Analysis

To meet global food demand, strategies promoting efficient water use are essential for sustainable agricultural practice. Deficit irrigation (DI) is currently promoted as a water-saving strategy, though reports on its effect on yield and water productivity (WP) remain inconsistent. To address this inconsistency, we conducted a meta-analysis on eight crops in Ethiopia: maize, wheat, sesame, bean, onion, potato, tomato, and pepper. We used climate, soil type, soil pH, irrigation method, crop type, and irrigation water amount as explanatory variables. As expected, the amount of irrigation water was found to be the primary factor influencing yield loss. Sesame, tomato, and wheat showed the greatest resilience to water stress even at low DI levels (50% crop water requirement (ETc)). Applying DI at 50 –70% of ETc in wheat increased WP by 48% with only a 16% yield loss. Similarly, in tomato, WP improved by 51% with a 21% yield reduction. Across all moderators, applying DI at 80% ETc was found to be statistically (p > 0.05) the same as full irrigation in terms of crop yield. Practicing DI with drip irrigation under DI levels below 80% ETc was not found to be promising, as it resulted in high yield loss (up to 45%) with minimal WP gain. In contrast, alternate and fixed furrow irrigation methods performed well at 70 – 80% ETc, maintaining low yield loss with significant WP improvement. These irrigation methods performed best at 100% ETc with 50% WP improvement and 18% yield reduction. These findings provide valuable insights for optimizing irrigation strategies and support informed decision-making for sustainable agricultural water management.