Research on Crop Irrigation Schedules Under Deficit Irrigation—A Meta-analysis

Increasing water consumption in agriculture due to global climate change has posed considerable challenges to food security, thus improving the efficiency of water production is the key to sustainable agricultural development. Deficit irrigation uses limited water resources to achieve stable crop yield according to the migration law of production parameters during crop growth. This study uses meta-analysis to quantitatively analyze the yield and water effects on winter wheat and summer maize under deficit irrigation in northern China based on previously published studies. The result shows that deficit irrigation results in an average yield reduction of 7.10% for wheat and an average yield reduction of 18.71% for maize, while the average water use efficiency (WUE) increases by 9.25% and 6.38% for wheat and maize, respectively. This research reveals the differences and effectiveness of deficit irrigation of wheat and maize in different regions and hydrological years and proposes appropriate water deficit levels and irrigation strategies. The optimal deficit irrigation schedule in different regions involves irrigating twice during the wheat growth with irrigation quotas of 100–200 mm. Generally, supplementary irrigation is carried out during the critical water demand period. When supplemental water (the sum of irrigation and precipitation) is 80% of full irrigation (FI), maize can obtain higher yield and WUE. This study provides a reference for irrigation strategies for winter wheat and summer maize in the major agricultural producing areas in northern China to mitigate the adverse effects of increased agricultural water use and extreme climates.