Properties of New Biodegradable Plastics for Mulching, and Characterization of their Degradation in the Laboratory and in the Field

One of the more important by-effects of Mediterranean Horticulture is the serious drawback of vast quantities of wastes caused by the extensive use of polyethylene. In order to identify an alternative to replace the polyethylene (PE) film for mulching, the aim of this work is to determine the potential of the recently emerged biodegradable plastics. A field trial has been conducted with a black mulched tomato crop in an organic production system. Three biodegradable plastics for mulching (Mater-Bi, Biofilm and Bioflex (Bi-opl)) were compared with PE. Spectro-radiometric and mechanical properties of the new materials were analysed in the laboratory and compared to those of PE. Plastic film degradation was monitored along the crop cycle by means of a qualitative scale. Also, plastic samples were taken and mechanical tensile tests were performed. For mulching, the new biodegradable materials proved to be competitive from a spectrometric point of view, both optical and thermal; their mechanical features were satisfactory for mulching, but below those of the PE film. At the end of the crop, Biofilm was degraded most, followed by Mater-bi and Bioflex. Polyethylene was scarcely degraded. The mulches field behaviour was in accordance with the mechanical tests results, which showed a rapid decrease along time of tensile strength and elongation at break for the three biodegradable films and not for PE. The degradation of the biodegradable materials tested did not negatively influence productivity, while it avoided the need of picking up and carrying the mulch to the landfill after use. It is concluded that the biodegradable plastics behave very similar to PE; degradation adds an additional value to these new materials.