Meta-analysis of crop water use efficiency by irrigation system in the Texas High Plains

A meta-analysis was performed on 351 studies from 17 articles published between 1990 and 2016 to determine how a water use efficiency (WUE) treatment is affected by irrigation systems and management practices on clay and clay loam soils in a semi-arid environment relative to a rainfed control. Several explanatory variables (moderators) were examined to determine their impact on WUE such as crop type, irrigation capacity, rainfall, soil type, planting time, and nitrogen application. Results were sub-grouped by irrigation system. Overall, the impact of irrigation system on WUE directly correlated with the efficiency of the irrigation system. Subsurface drip and center pivot irrigation systems had the largest impacts on WUE with increases of 147 and 99%, respectively, compared to a 14% increase under furrow irrigation. Corn (Zea mays L.) had a higher response to WUE in subsurface drip irrigation (260%) compared to center pivot irrigation (46%), whereas WUE in cotton (Gossypium hirsutum L.) had a 71% change in center pivot systems compared to 63% under subsurface drip. The biggest increases in WUE relative to a rainfed control were for sorghum (Sorghum bicolor (L.) Moench), which had a 13% change under furrow irrigation, 160% change under center pivot and 341% under subsurface drip.