Two-dimensional numerical simulations of soil-water and heat flow in a rainfed soybean field under plastic mulching

Abstract

Numerical simulation can help understanding waterand heat-flow systems through plastic-mulched soils. An effective simulation approach is crucial to know the role of plastic mulch in a soil ecosystem, which can save water in agriculture. A field experiment was conducted at Gifu University in a rainfed soybean cultivation under plastic mulch and bare soil treatments to clarify the soil water and heat flow mechanism. Furthermore, the two-dimensional numerical software HYDRSUS-2D model with different boundaries at the soil surface was used to simulate water and heat flows. Firstly, soil hydraulic parameters were estimated by inverse solution using laboratory-measured data and then coupled soil-water and heat flows were simulated by optimizing soil thermal parameters by inverse solution. The HYDRUS-2D model simulated water and heat flow through the root zone depths satisfactorily. The root-mean square error (RMSE) was 0.015–0.030, and 0.046–0.055 cm cm 3 for the plastic mulch, and bare soil, respectively, in estimating soil moisture and 0.66–1.28, and 0.70–1.54 C, respectively in estimating soil temperature. Water infiltration was 61% lower in the plastic-mulched soil, which reduced soil evaporation as well as soil-moisture storage changes compared to bare soil. This study can be applied to design and manage different plastic mulching patterns in rain-fed crop cultivation.