Films of biodegradable blends based on sodium alginate for applications in agriculture, as films for the solarization of soils, were prepared and characterized in terms of the mechanical parameters and optical properties. The films analyzed in this study were transparent in the visible region and opaque in the infrared region. This ensured a micro greenhouse effect on the soil. One of the films was also characterized optically in the ultraviolet-visible-infrared region. The optical data were analyzed with a theoretical model, which was able to predict the temperature of the soil at different depths and at different times of the day. The susceptibility time of the film was compatible with its use in agriculture as a film for solarization. (c) 2005 Wiley Periodicals, Inc.