Integrating rainwater harvesting and drip irrigation for water use efficiency improvements in apple orchards of northwest China

Rainwater harvesting and drip irrigation are commonly used water saving techniques ensuring agricultural sustainability in drylands of northwest China. However, few studies have compared the advantages and shortcomings of these two techniques. A meta-analysis of 22 study cases across four provinces/regions in northwest China (i.e., Shaanxi, Ningxia, Gansu, and Xinjiang) was conducted. The effects of varied rainwater harvesting and drip irrigation techniques on apple yield, soil water storage, and water use efficiency were evaluated. Results showed that 38.5 % apples (by weight) are produced in northwest China currently. Drip irrigation could improve apple yield by 54.3 %, even more so than rainwater harvesting which offered a 19.1 % improvement. For rainwater harvesting, plastic film mulching was more effective for improving apple yield than grass mulching. Compared with control values, rainwater harvesting can increase 0–200 cm soil water storage by 13.7 %. Optimized drip irrigation methods, such as partial root-zone drying and infiltration enhancing pipe, can enhance water use efficiency by 17.2 %. This study highlights the importance of integrating rainwater harvesting and drip irrigation techniques for improving water productivity, preventing land degradation and desertification, as well as eradicating poverty in arid regions.