Simulation of soil water and heat flow in ridge cultivation with plastic film mulching system on the Chinese Loess Plateau

A widespread measure for improvement of soil water use efficiency (WUE) in the semi-arid region of China is ridge cultivation with plastic film mulching system. However, the modification of soil water and heat flow under this management system is not well understood. The objective of this study was to understand soil water and heat coupling processes by monitoring and modeling of soil water and temperature dynamics in this system that is commonly used on the semi-arid Chinese Loess Plateau. Four treatments were investigated: conventional fertilization (CK, control), recommended fertilization (RF), straw mulching based on RF (SM), and straw mulching in furrows plus plastic film mulching on soil ridges based on RF (FM). Based on the field monitoring results, the process-based model HYDRUS-2D was calibrated to simulate the soil hydrothermal processes for the different treatments, each represented by specific boundary conditions at the soil surface. The model simulations have a good agreement with the field observation, showed that there are significant differences in soil water contents (5%) among the four treatments, with the FM treatment having the highest water storage and the highest WUE. While soil daily mean temperature was very similar, the daily temperature fluctuations were significantly higher under the plastic film mulching compared to the other treatments. The FM treatment performed better during the cold year than a warm year, improved crop production and water resource use through reduced evaporation and elevated transpiration. The modeling approach presented here is an efficient way to clarify the mechanisms of root-zone water and temperature dynamics under mulching and/or tillage that could be adopted for optimizing soil hydrothermal management in this region.