The ridge and furrow rainfall harvesting (RFRH) system collecting runoff by the plastic mulched ridges is a useful method to improve crop productivity in northwest China. We performed a field study where the RFRH system was combined with irrigation (RI) to reduce water irrigation use and to increase the crop water use efficiency (WUE) in a semi-humid climate. The amount of irrigation using RI was reduced by half compared with traditional furrow irrigation (FI) and border irrigation (BI) due to its rainwater harvesting effects. Our results showed that the RI treatment effectively alleviated drought stress during key periods of crop growth. At the jointing stage, the soil water storage in the 0-200 cm soil layer was increased by 2.82-8.02% and 2.25-8.40% compared with Fl and BI, respectively, and the soil water consumption by maize below 60 cm was significantly decreased at the tasselling stage. With RI, the harvest biomass, grain yield, and WUE were significantly increased by 14.59-19.93%, 5.33-7.01%, and 12.21-18.01% compared with Fl, respectively, and compared with BI, these values were significantly increased by 24.48-27.25%, 8.83-11.23%, and 14.99-22.91%, respectively. The irrigation amount was reduced by 1500 m(3) hm(-2), and the irrigation WUE with RI was 2.1 and 2.2 times higher than that using Fl and BI. The irrigation water productivity was improved by 1.71 and 5.70 times compared with Fl and BI, respectively in 2011. These results suggest that combining the RFRH system with irrigation is suitable for reducing irrigation water use by enhancing the efficient utilization of local rainfall, which could have very important applications in irrigated fields in semi-humid or semi-arid areas. (C) 2015 Elsevier B.V. All rights reserved.