A new solution of high-efficiency rainwater irrigation mode for water management in apple plantation: Design and application

Due to the lack of stable irrigation water sources and low rainwater utilization efficiency, soil water deficit has become the main factor restricting the sustainable development of the apple industry in the Loess Plateau. The scientific and efficient use of rainwater for irrigation may provide a new solution to alleviate the regional soil water deficit. Rainwater is the only water source for the growth of apple trees, and whether it can be used as a stable and sustainable irrigation water source should be quantitatively considered. At present, there is still a lack of quantitative data to support whether rainwater can meet the irrigation needs of apple orchards. In this research, rainwater harvesting technology is combined with a solar intelligent irrigation system equipped with soil moisture sensors to form a high-efficiency rainwater irrigation (HRI) mode suitable for dryland apple orchards. Through practical application, this study found that HRI mode can effectively improve the soil drought of 0–200 cm and keep the soil water content in a relatively stable range during the apple growth period. Compared with only using rainwater harvesting technology and combined with traditional irrigation methods (SDI), HRI mode can increase apple yield by 56.2% and 22.0%, WUE by 40.4% and 12.6%, respectively. With the increase of apple yield, HRI mode has good economic feasibility, and its economic recovery period is 2 years. On the regional scale, this study selected irrigation guarantee rate and solar energy resources as evaluation indicators to further divide the areas suitable for rainwater irrigation in apple-cultivating region on the Loess Plateau. The area where the irrigation guarantee rate of rainwater was greater than 75% is 1.22 × 10⁷ m², accounting for 47.6% of the total area. This means that apple production in the Loess Plateau can increase by approximately 549.8 tons/year, save 1.5 × 10⁴ m³ of irrigation water resources, and increase WUE by about 33.4%. Under the two different future climate scenarios (RCP 2.6 and RCP 8.5), the area accounted for 49.7% and 57.2% respectively, which was higher than the current situation. The areas with high rainwater irrigation guarantee rates are mostly concentrated in the central and southern parts of the apple-cultivating region. To maintain the sustainable development of the orchard ecological environment, areas with insufficient rainwater should assist other water management measures. In conclusion, high-efficiency rainwater irrigation can effectively alleviate the water contradiction in apple-cultivating region. In future agricultural water management, more attention should be paid to precision rainwater irrigation to ensure the coordinated development of agricultural economy and ecological environment.