Effect of Plastic Film Colours and Perforations on Energy Distribution, Soil Temperature, and Evaporation
Zunqiu Xu, Rony Wallach, Song Jian, Xiaomin Mao
Abstract
Plastic film mulching is a commonly used agricultural measure in arid/cold regions to improve crop growth. Despite previous studies on the impact of film mulching on soil water/heat status and crop growth, it is not clear how plastic film colours and perforations affect energy distribution, soil temperature, and evaporation. Six sets of column experiments were performed with three plastic film colours: transparent (T), black (B), and silver-grey (G), and two perforation ratios: 4.49% and 21.44%, to monitor soil evaporation and soil/film mulching temperature. Using these two main control factors, a soil–mulch–atmosphere system (SMAS) model was established to simulate soil evaporation and energy distribution. The simulations of soil evaporation compared well with the measurements. The available net energy was positively related to the perforation ratio and transmittance of the plastic film, which further influenced soil temperature and altered energy distribution. Both simulated and measured results gave the following order for transpiration with the plastic films: T > B > G. The SMAS model was more accurate when a mulch with weak light transmittance covered the field. Moreover, by comparing simulated evaporation mass loss with and without considering heat conduction between the plastic mulch and the soil surface, Csm, we found that it is feasible to exclude Csm. However, Csm is indispensable in the SMAS model for understanding the mechanism of plastic film mulching in agroecosystems, particularly at night.