Can rainwater harvesting replace conventional irrigation for winter wheat production in dry semi-humid areas in China?

The plastic-mulched ridge and furrow rainwater harvesting (PRFRH) planting practice is widely used in rain-fed arid and semi-arid areas. However, it remains unknown whether PRFRH can replace or reduce irrigation to achieve a high and stable wheat yield in dry semi-humid areas. In this study, two cultivation practices (PRFRH and conventional flat planting [CK]) were used in combination with three irrigation regimes (0, 75, and 150 mm) to evaluate the efficacy of PRFRH in different precipitation year types (dry, normal, and wet years). Results showed that PRFRH increased soil temperature and pre-jointing soil water storage at 0–80 cm depth, whereas irrigation increased post-anthesis soil water storage at 0–80 cm depth. Furthermore, PRFRH prolonged the duration of the jointing–anthesis stages and thereby increasing the kernel number. Both PRFRH and irrigation increased dry matter accumulation and the leaf area index. PRFRH accelerated the grain-filling rate but shortened the effective grain-filling duration, while irrigation extended the effective grain-filling duration. PRFRH did not significantly influence kernel weight, whereas irrigation increased kernel weight. Overall, PRFRH reduced the effective wheat planted area and thereby reducing spike number, although it increased the kernel number, resulting in yields that were 13.7% lower than those under CK. The yield under PRFRH was significantly higher than that under CK only in the dry year but lower in the normal and wet years. Irrigation increased the yield; however, the yield did not significantly differ between the 75 and 150 mm irrigation regimes. The water productivity and net profit under 75 mm irrigation were relatively high. In conclusion, in dry semi-humid areas, PRFRH combined with a 75 mm irrigation volume could mitigate drought stress to improve yield, water productivity, and net profit in dry years only.