Evaluating the potential of biodegradable films as alternatives to fossil fuel-derived plastic mulches for weed control in an organic field vegetable system

Plastic mulches are increasingly used in vegetable production systems where they are a cost effective means of weed control. However they are usually made from fossil fuel-derived plastic and so there is concern about the environmental implications of their production, use and disposal. This paper describes two trials that were conducted in the UK in 2019 under organic management to compare a durable woven polypropylene mulch, a polyethylene film mulch, two commercial GM-free corn starch biodegradable film mulches and two innovative potato starch biodegradable film mulches with weeded and unweeded controls. In the trial with onions as a test crop the weeds were very competitive and quickly overwhelmed the crop both in unweeded controls and when using mulches that were easily damaged by weeds that grew beneath them. In the trial using cabbages as the test crop the more fragile mulches were able to suppress the weeds during the critical early growth period until the plants became competitive. Plant based biodegradable film mulches have an environmental cost in terms of the inputs needed to grow, process and transport them. More research is needed to evaluate the potential of locally sourced mulch materials such wood chips from agroforestry systems and to continue to develop better biodegradable materials.