Coupling effects of plastic film mulching and urea types on water use efficiency and grain yield of maize in the Loess Plateau, China

• Plastic film mulching stores more soil water and produces more grain yield.
• CRF improves the water and nitrogen use efficiency and grain yield than urea.
• PMb combined with CRF gives higher maize yield and water use efficiency.

Increasing water and nitrogen use efficiency is important for sustainable agricultural development, especially in arid and semi-arid areas. A two-year field experiment was conducted to investigate the effects of field management practices on soil water, maize development, and yield on the Loess Plateau, China. The experiment adopted a split-plot design, with three mulchings as the main-plot treatments and two urea types (225 N ha−1) as the sub-plot treatments. Treatments were established as: (1) no plastic film mulching with urea (NU), (2) no plastic film mulching with controlled release fertilizer (NC), (3) white plastic film mulching with urea (WU), (4) white plastic film mulching with controlled release fertilizer (WC), (5) black plastic film mulching with urea (BU), and (6) black plastic film mulching with controlled release fertilizer (BC). The soil water storage was higher under black plastic film mulching than that under other treatments for most sampling dates within the two experimental years, especially in the second maize growing season. Higher soil water stimulated maize growth, as indicated by a higher plant height, leaf area index, and greater biomass accumulation; thus, the highest grain yield (16.64 t ha−1) and water use efficiency (28.3 kg ha−1 mm−1) in 2014 was recorded in BC plots, which were higher by 34.5% and 34.8%, respectively, compared with those in NU. White plastic film mulching also increased the soil water content and promoted maize development, grain yield, and water use efficiency; thus, higher grain yield (16.02 t ha−1) and water use efficiency (26.5 kg ha−1 mm−1) were recorded in WC plots in 2014. In the two experimental years, controlled release urea treatments always produced significantly higher maize yields than conventional urea treatments, except the NC plots in 2013. However, significant soil water depletion in the deeper (>120 cm) soil layers was detected at harvest time in 2014 under BC treatment, indicating that higher yields might not be sustained in long time periods. In conclusion, plastic film mulching, particularly black plastic film mulching combined with controlled released fertilizer, could improve the water use efficiency and suitably meet the nitrogen requirements of maize, thereby increasing the grain yield in the Loess Plateau, China.