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Plastic Mulch

The mountain of waste plastic from
just one field, creates a waste problem
Photo by Cheryl EmpeyPlastic mulches have been used in horticultural vegetable production since the 1960s. In the early days the problem of disposing of the plastic was solved by simply dumping it at the local landfill site. Farmers even joked that the local councillor had a dump truck that was loaned to the local farmers for that purpose. This soon changed and farmers were presented with the reality of the amount of plastic that was being used and then dumped. For many farmers, the solution was to dump the plastic illegally, in gullies, creeks or by trying to dig a hole big enough to burry it.

The Benefits of Using Plastic Mulch

Plastic is laid over the bed and
held down on each side with soilThere are many benefits of using plastic mulch, including soil temperature modulation, enhanced produce quality, improved soil water management by reduced evaporation, reduced fertilizer leaching, earlier crop production, higher yields, reduced soil erosion, better management of certain insect pests and fewer weed problems. Plastic mulches are quite inexpensive and there are well developed crop management systems including tractors and other machinery specifically designed to work with and through plastic mulch.

Disadvantages of Plastic Mulch

Unfortunately, problems with dumping
the plastic waste result
in inappropriate dumpingThe use of plastic mulch has a massive negative environmental impact. Plastic is made from petro-chemicals, which are non-renewable, release toxins in their manufacture, use and waste, they are not biodegradable and huge amounts of plastic result from horticultural practices using plastic mulch. Mulch is generally used for only one season before being discarded. The typical methods for disposal are incineration (emitting toxic chemicals into the atmosphere), burying it in landfill or recycling. Open burning of plastic is not allowed in almost all jurisdictions so incineration is an alternative, especially where the fuel value can be recovered. Unfortunately these facilities are not widely available. Landfill was a popular option, but most landfill sites do not accept used plastic mulches. Landfill is not a sustainable solution considering the time it takes for plastic to break down. Recycling is difficult due to the organic, moisture, and chemical residues associated with used plastic mulch.

Alternatives to Plastic Mulch

Yes, these workers are wearing
protective gear for a reasonThere are two main alternatives to plastic mulch; an organic mulch and biodegradable plastic mulch. Using an organic mulch is a viable option in warmer climates where the warming effect of plastic mulch is not required. A cover crop is grown between crop seasons and them rolled to create a thick cover of organic matter into which the next crop is planted. This technique adds organic matter to the soil, improves soil structure (when used in combination with low till and controlled traffic farming), controls weeds (perhaps not as effectively as plastic mulches) and improves soil moisture levels. Cover crops are more effective at managing erosion than plastic mulches as water is absorbed into the soil profile, rather than running off the plastic mulch and causing a problem elsewhere.

The other alternative is using a biodegradable plastic mulch. Plastics can be made from non-petrochemical substances. Plant plastics can be made from plant starch however the cost of making these biodegradable plastic prohibit their use as an agricultural mulch.

Plastic is a massive problem for the environment. In Australia around 1 million tonnes of plastic materials are produced each year and a further 587,000 tonnes are imported. Packaging is the largest market for plastics, accounting for over a third of the consumption of raw plastic materials - Australians use 6 billion plastic bags every year!