Photo: Megan Chawner
There's been a lot of buzz about biodegradable and compostable mulch, but how do you know one of these might be a good choice for your operation?
Let's start by considering why mulch is used widely by growers in Pennsylvania. Mulch can increase yields, produce high quality, earlier maturing crops, enhance insect management, and control weeds. This system also allows the use of other components, such as drip irrigation, to increase efficiency.
Traditionally, plastic mulch is used in vegetable and berry production. It comes in a variety of thicknesses and colors that farmers can choose between for their specific needs. Black plastic is the most widely used mulch color and is typically the least expensive option. However, additional grower costs for removal and disposal should be taken into account. The use of plastic mulch also raises environmental concerns since it is a petroleum-based product and difficult to recycle.
Things get more complicated when we look at degradable mulch options. There are several different kinds, made with a variety of materials. The first and least popular degradable mulch is photodegradable plastic mulch that breaks down when exposed to light. Another type of degradable mulch is made primarily of polyethylene.These mulches degrade very slowly in the environment. Many growers who use these products report uneven and incomplete breakdown, particularly after tillage when the plastic fragments are buried at the end of the season.
Options that are more popular include biodegradable and/or compostable mulch. Most biodegradable mulch is made from plant starches such as corn and wheat. Soil microbes are able to break down the starch completely into CO2 and water. As a result, the mulch can be tilled in at the end of the season, which reduces labor and disposal costs. However, these mulches can cost two to three times as much as standard black plastic.
It is important for organic growers to note that in 2015, the National Organic Program added an allowance for the use of biodegradable mulch, but specified that it must be 100% bio-based. However, due to the physical limitations of starch, including its brittleness, it must be blended with polymers and plasticizers. Since most, if not all, of the commercially available biodegradable mulch contain some petrochemicals (and are typically less than 50% bio-based), there are no biodegradable mulch products on the OMRI list.