In order to analyze the effect of plastic mulching on water use efficiency of spring hybrid millet (Setaria italica), field experiments were conducted during the 2012 growing season, at an experimental station located in a semi-arid region of North China. Four treatments were applied: (i) plastic mulching of ridges and furrow sowing (T1), (ii) ridges and furrows without plastic mulch (T0), (iii) flat soil with plastic mulch (A1), and (iv) flat soil with no plastic mulch (A0) (control). Dynamics of soil moisture and soil temperature, together with crop growth, were monitored continuously in both mulched and unmulched fields. Changes in water consumption, soil temperature, and plant growth and development were analyzed. Results indicated that plastic mulching produced a 2–5-day advance in emergence of each growth stage. Soil temperature at 0–15cm depth increased by 1.25°C and 0.84°C under mulched treatments A1 and T1, respectively, while soil water content at a depth of 0–10cm increased by 1.42% and 1.29% in the same treatments. Leaf area index and plant height were also significantly higher in plastic-mulched treatments, except in later growth stages. Because plastic mulching improved tiller and ear numbers significantly, grain yield increased by 13.25% and 6.64%, in Al and T1 treatments, respectively. Water use efficiency at yield levels of plastic-mulched A1 and T1 plots was 24.44% and 3.6% higher than in unmulched flat and furrowed plots, respectively. Plastic mulching significantly reduced water consumption, retained soil water content, and increased soil temperature, to promote spring hybrid millet germination, and increased tiller numbers, and consequently, aboveground dry matter; it eventually significantly improved grain yield and water use efficiency. Plastic film mulching produced greater grain yield, water use efficiency, and benefits when used in flat planting patterns.
