Effects of plastic mulch on soil heat flux and energy balance in a cotton field in Northwest China

Abstract

Surface energy balance (SEB) is a basic principle for all of the atmospheric circulation models, and surface soil heat flux (G0) is an important component of energy balance. Plastic mulch is widely used in arid regions and alters land surface processes. In this study, hourly/daily G0 and SEB over a mulched cotton field were analyzed in Northwest China. The net radiation beneath the mulch was simulated using transmitted down short-wave and down long-wave radiation through the mulch and up short-wave and up long-wave radiation from the soil beneath mulch. The results show that: (1) on the hourly time scale, G0 in mulched soil is much smaller than that in non-mulched soil, day and night. This implies that mulch prevents energy going into the soil during the daytime and reduces soil heat loss at night. On the daily time scale, G0 is similar in mulched and non-mulched soil. (2) During the seedling emergence period when the cotton is small, the energy balance closure over mulched soil (0.79) is slightly smaller than that over non-mulched soil (0.81). (3) Comparing to soil temperature in non-mulched soil, there's a time offset on soil temperature in mulched soil at the same depth, which will bring a hysteresis on G0 and SEB.