Evapotranspiration partitioning, water use efficiency, and maize yield under different film mulching and nitrogen application in northwest China

Exploring the effects of film mulching and nitrogen (N) on crop transpiration (Et), soil evaporation (Es), crop actual evapotranspiration (ETa), and their relationships with yield and water use efficiency (WUE) is vital to improve understanding of crop water consumption and production. A 3-year (2017―2019) maize field trial was designed with three film mulching patterns (flat planting without mulching (FPNM), ridge-furrow with biodegradable film mulch over the ridge (RFBM), and ridge-furrow with plastic film mulch over the ridge (RFPM) as main plots and N application levels (0 and 180 kg N ha–1) as subplots. The results showed that RFBM and RFPM increased Et more than FPNM when no N was applied. However, the Et increment for FPNM was higher than for RFBM and RFPM during the 2017 (dry) and 2019 (wet) seasons when N was applied. Both RFBM and RFPM decreased Es, ETa, and the total Es / ETa ratio compared with FPNM, regardless of N application, and improved yield and WUE when no N was applied across all three seasons. Applying N to RFBM and RFPM significantly improved yields in 2017 and 2018 (normal) seasons and increased WUE across all three seasons compared with FPNM. However, in 2019, maize yields were 4.68% and 4.48% higher in FPNM than in RFBM and RFPM when N was applied. Nitrogen mainly increased Et during the reproductive stage in FPNM and RFPM, but increased Et during the mature stage in RFBM. In contrast, N for three planting patterns decreased Es at the seeding and filling stages but increased Es at the jointing and mature stages during the 2017 and 2018 seasons. However, in the 2019 season, N application decreased Es in FPNM and RFBM, but increased Es in RFPM. N application also improved yield and WUE by 23.37–59.56% and 23.78–60.36% across the three seasons, respectively. Thus, RFBM and RFPM are recommended for maize production in northwest China, and RFBM with N application can replace RFPM in dry and wet seasons.