Soil thermal response under plastic covers III. Simulation

Enrique Misle A.1 y Aldo Norero Sch.2

A simplified simulation model was developed to predict soil temperature under plastic covers based on the numerical solution of the soil heat flow equation. This method requires the definition of the boundary conditions, which at the soil surface are solved through the radiation and energy balance. Also it considers the heat partitioning ratio and the albedo of the soil surface covered with plastic film. This parameter is variable according to the time of the day. Thus the soil surface temperature was estimated and treated as if it were identical to the temperature of the plastic. To start the simulation process and to determine the soil profile temperature, a periodic function combining the analytical solution and a Fourier analysis with four elements (k = 4) was used. The temperature at 30 cm depth was considered constant for the model scale, which was experimentally confirmed. A computer program was elaborated that would operate at different time lapses and depth spacing according to soil thermal diffusivity. The assumption that plastic sheet was in direct contact with soil surface led to acceptable agreement between simulated and experimental results. However, it was also necessary to modify the values of surface emissivity and this remains a point needing further elucidation.

Keywords: soil temperature, simulation model, plastic mulch, solarization
1 Universidad Católica del Maule, Facultad de Ciencias Agrarias y Forestales, Escuela de Agronomía, Casilla 278, Curicó, Chile. E-mail: emisle@hualo.ucm.cl
2 Pontificia Universidad Católica de Chile, Facultad de Agronomía e Ingeniería Forestal, Escuela de Agronomía, Casilla 306 - 22, Santiago, Chile.