Transparent plastic film combined with deficit irrigation improves hydrothermal status of the soil-crop system and spring maize growth in arid areas

Plastic film mulching and irrigation amount greatly affect soil hydrothermal status and spring maize (Zea mays L.) productivity in arid areas. Yet the coupled effects of film mulching with different optical properties and deficit irrigation on water and temperature variation within the soil-crop system and on plant growth in arid areas have not been well-investigated. A two-year field experiment was conducted with five treatments: 1) full irrigation without mulching (FN), 2) full irrigation with transparent plastic film mulching (FT), 3) full irrigation with black plastic film mulching (FB), 4) deficit irrigation with transparent plastic film mulching (DT), and 5) deficit irrigation without mulching (DN). The results showed that plastic film mulching significantly increased soil water in the 80–120 cm soil layer and canopy air humidity. The alternating wet-dry behavior of soil water caused by plastic film mulching was an effective water utilization strategy that increased crop water productivity. DT stimulated the alternating wet-dry behavior of soil water in the 0–80 cm layer more than the FN. This alternating behavior was characterized by relatively wet soil at the 12-leaf growth stage (V12), relatively dry soil from V12 to the grain-filling growth stage (R3), and relatively wet soil again after R3. Alternating wet-dry behavior changed from wet to dry at V12 in 2019 and was earlier than V12 in 2020. Plastic film mulching significantly increased soil temperature at the six-leaf growth stage (V6) and decreased canopy air temperature during the whole maize growing seasons. The higher net photosynthesis rate was observed at the canopy air relative humidity of 78.6%. Net photosynthesis rate decreased with increasing canopy air temperature. FT, FB, DT, and FN significantly increased grain yields over DN by 39.7–45.8%, 25.5–41.8%, 18.2–33.4%, and 9.0–17.0%, respectively, and increased net income over DN by 894–1127, 436–979, 343–844, and 166–429 USD ha–1, respectively. DT decreased net income and output/input ratio by 28.1% and 10.9% in 2019, respectively, compared with FT. However, these values were 12.3% and 4.0% in the relatively wet growing season in 2020. Deficit irrigation combined with transparent plastic film mulching can ensure an acceptable maize grain yield and net income in arid areas with limited water resources, especially in growing seasons with greater rainfall.