Numerical Modeling of Soil Water-Heat Transport under Oxo-Biodegradable Film Mulch and the Optimal Mulching Period

Timely monitoring and regulation of the transport and distribution of soil water and heat are appropriate methods to ensure and improve crop yields. With the degradation of the oxo-biodegradable film, the upper boundary condition is a time-variable boundary, and soil water-heat transport is more complicated, comparing with conventional plastic film. Based on HYDRUS-2D version 2.02 and the characteristics of mulching films, a soil water-heat coupled transport mathematical model of drip irrigation was established, and the simulated soil water content and temperature were tested against three-year field observations for calibration and validation purposes. The model prediction demonstrated that the induction periods of oxo-biodegradable film mulching differed in different hydrological years. In normal flow years, an induction period of 50-80 days had higher water use efficiency. While the window would increase to 50-100 days in low flow years. As for temperature, comparing with conventional plastic film mulching, the decreasing trend of temperature started to slow down when the induction period increased to 70 days. Therefore, the optimal induction period of the oxo-biodegradable film is 50-70 days.