Optimized ridge–furrow with plastic film mulching system to use precipitation efficiently for winter wheat production in dry semi–humid areas

Ridge–furrow with plastic film mulching (RFPFM), a rainwater harvesting system, is receiving increasing attention worldwide. However, its usefulness in semi–humid regions with irrigation capabilities remains unclear. In addition, the optimal ridge–to–furrow ratios and nitrogen (N) application rates are unknown. In this study, we investigated five different planting patterns (i.e., rain–fed flat planting [CK], RFPFM practices with three different ridge–to–furrow ratios [20:40, RFPFM20; 30:30, RFPFM30; and 40:20, RFPFM40], and RFPFM plus supplemental irrigation [RFPFM + SI]) under two N application rates (75 and 225 kg·ha–1) in winter wheat over two years. RFPFM practices led to increased soil temperature in the ridges at the seedling stage and the retention of more water in the furrows throughout the two growing seasons. The improved hydrothermal characteristics of RFPFM plots led to early and stable seedling establishment, resulting in higher grain yields, water use efficiency (WUE), and net revenues. Grain yields were higher with RFPFM20, RFPFM30, RFPFM40, and RFPFM + SI practices than with CK by 28.3%, 37.2%, 55.6%, and 100.4%, respectively, averaged for both N rates over the two years. Additionally, WUE was higher by 22.6%, 28.3%, 40.5%, and 9.3%, respectively. Increased ridge–to–furrow ratios affected micro–topography, as evidenced by improvements in hydrothermal features, grain yields, WUE, and net revenues. Overall, we recommend RFPFM40, the widest ridge, as a promising water–saving and economical practice for winter wheat production in dry semi–humid areas. Supplemental irrigation could be considered in RFPFM practices to alleviate drought stress in dry years (<150 mm precipitation) to increase grain yields, WUE, and net economic benefits. Technological advancements, such as innovative mechanization to reduce extensive labor costs, are required to boost the adoption of RFPFM practices, fully exploit its economic and social benefits, and prioritize environmental sustainability.