Assessing the effects of plant density and plastic film mulch on maize evaporation and transpiration using dual crop coefficient approach

Plastic film mulching, in combination with high plant density, is a common practice for rain-fed maize production, especially in Northeastern China. To explore effects of plant density and plastic film mulching on the evapotranspiration of maize during its different growth periods, a two-year split-plot field experiment with non-mulching (M0) and plastic film mulching (M1) and three plant densities (60,000 (D1), 75,000 (D2), and 90,000 plants ha(-1) (D3)) was conducted at a site of Shenyang located in the Northeast China in 2016 and 2017. Based on the field experimental data of spring maize, water balance equation and dual crop coefficient method were adopted to explore effects of plant density and plastic film mulch on evapotranspiration of maize at different growing stages. The results showed that compared with non-mulching treatment, the plastic film mulching increased maize transpiration by about 20.0%-32.0% and 3.5%-15.4% and reduced soil evaporation by 51.8%-63.0% and 21.5%-39.5% in 2016 and 2017, respectively. Overall, the mulching treatment significantly reduced maize water consumption by about 12.4% and 6.2% in 2016 and 2017, respectively. The mulching treatment also increased the basic maize crop coefficient by 0.03-0.07 and reduced the average evaporation coefficient by 0.14, compared with non-mulching treatment. In addition, compared with non-mulching, plastic film mulching increased ratio of transpiration by 19%-32% and 5%-12% in 2016 and 2017, respectively. For effects of plant density on maize evapotranspiration, higher plant density resulted in more evapotranspiration during the whole growth season of maize except for its initial growth stage. The average evapotranspiration of D1-D3 treatments from two growing seasons of maize were 469.2, 509.6 and 534.1 mm, respectively. For evaporation and transpiration, the maize transpiration increased with the increase of planting density, and the maize evaporation increased with the increase of planting density under plastic film mulching conditions but decreased with non-mulching treatment.