Vertical rotary sub-soiling under ridge–furrow with plastic mulching system increased crops yield by efficient use of deep soil moisture and rainfall

Recently, the technology of combining vertical rotary sub-soiling (VRT) with ridge–furrow construction with plastic film mulching system (RFMS) has become a promising solution to improve soil water characteristics and crop yields in the semi-arid Loess Plateau, China. However, the effect of this technique on deep soil moisture and rainfall utilization to enhance the crop yield is unclear. To investigate this, two field experiments (2016–2017) were set up with maize and potato as research objects. There were four tillage practices under RFMS for maize: (1) MVT, VRT to a depth of 40 cm; (2) MST, sub-soiling to a depth of 40 cm; (3) MTT, rotary tillage to a depth of 15 cm; and (4) MZT, zero tillage. There were three tillage practices under RFMS for potato: (1) PVT, VRT to a depth of 40 cm; (2) PST, sub-soiling to a depth of 40 cm; and (3) PTT, rotary tillage to a depth of 15 cm. Our results showed that the VRT under RFMS mainly significantly reduced soil water storage (SWS) in the 0–100 cm profile at the flowering stage, and SWS in the 100–300 cm profile of maize and SWS in the 100–200 cm profile of potato at the harvest stage compared with other tillage practices. This increased evapotranspiration (ET) throughout the whole growth stage and indicated that VRT promoted the utilization of deep soil water (below 100 cm) for maize and potato. The increase of ET and utilization of deep soil water contributed to promote crop growth, directly improved chlorophyll content, accelerated dry matter accumulation and prolonged the duration of the maximum dry matter accumulation rate, resulting in higher water use efficiency (WUE), harvest index (HI) and yield. The results suggested that VRT under RFMS improved WUE by 3.5–14.6%, HI by 2.8–23.85% and yield by 12.1–47.4% of maize compared to the other treatments and correspondingly by 18.9–92.3%, 1.6–29.6%, and 24.7–156.8% for potato. In addition, VRT significantly improved fallow efficiency by 56.3–133.1% and precipitation use efficiency (PUE) by 12.1–47.4% for maize, and correspondingly by 101.9–272.7% and 24.7–156.8% for potato, compared with other treatments. These data indicated VRT can improve the efficiency of precipitation preservation and utilization in RFMS. Overall, VRT can efficiently utilize deep soil moisture and rainfall to promote crop growth under RFMS，thereby, significantly increased maize and potato yields.