Comparison of biodegradable mulch products to polyethylene in irrigated vegetable, tomato and melon crops
Vegetable growers in the Dry Tropics of Queensland have been using drip irrigation and fertigation systems, in combination with polyethylene mulch film and seedling transplant technology for many years. Polyethylene mulch conserves water, suppress weeds and improve crop yields and product quality. However, the disposal of polyethylene mulch at the end of its useful life remains an intractable problem for growers and is considered a major environmental issue by the Industry. Options for mulch disposal are becoming increasingly untenable around Australia, with municipal authorities rejecting, restricting or increasing the costs of dealing with plastic mulch at their waste management facilities. There have been many proposed solutions trialled over the last two decades, with varying levels of success, but very low adoption. In an effort to solve the agricultural plastic waste dilemma, Bowen and Gumlu vegetable, tomato and melon growers have been trialling biodegradable mulch film products alongside Queensland Department of Agriculture, Fisheries and Forestry researchers. The project, funded by Bowen-Gumlu Growers Association, Horticulture Australia, mulch manufacturers and the Queensland Government, aimed to identify replacements for traditional polyethylene films and accelerate grower uptake of practical solutions. A number of products have been evaluated during this project, to identify potential replacements for polyethylene mulch films in irrigated vegetable production. These replacement films need to have the same desirable traits, with the benefits of no disposal issues and costs. Mater-Bi(c), a biodegradable product produced by Novamont and marketed by Australian Bio-Plastics, has been the most successful product to date. Mater-Bi(c) complies with Australian Standard AS 4736 ‘Biodegradable plastics suitable for composting and other microbial treatment’ and was evaluated against traditional plastic products with admirable results. Yields of honeydew melon, rock melon, capsicum, tomato, eggplant and chilli transplanted into Mater-Bi(c) were comparable with those grown in polyethylene films and provided good weed suppression for the life of the crop. The handling and laying of biodegradable products is slightly different to traditional plastic products. To keep costs down, 12 and 15 micron thicknesses are used, instead of 20 to 25 micron in polyethylene. It is important to handle these thinner films with care and use as soon as practicable. Thicker biodegradable films may be more suited to stony or cloddy soils.