October 15, 2012

Mulch. While it might seem like a garden afterthought, eliciting images of fresh woodchips applied to blossoming flower beds, it plays a critical role in edible gardens and farm plots.

Mulching is done in fruit and vegetable production for a number of reasons. You can use it to stamp out unwanted weeds and promote healthy crop growth. Mulch also holds in soil moisture—meaning less irrigation for you—and reduces water runoff and wind erosion. A properly mulched garden bed will likely face fewer soil-borne diseases and the plants will be less susceptible to rot; plus, the material will break down and contribute to your soil’s organic matter.

What Makes Mulch?

Don’t let your thoughts of mulch end with woodchips. You can find an array of mulches to suit your gardening needs, from organic mulches, such as grass clippings, hay and straw, to inorganic mulches, such as crushed rock, pea gravel and plastic sheeting. While you can purchase mulch materials through your local garden center or through a mass merchandiser, you can also make it yourself using materials found on your farm.

“Anything organic in nature is fair game as a mulch,” says Robert Polomski, environmental horticulture specialist at Clemson University. “I like to shred the material prior to using it. Shredding helps keep the mulch in place and increases its surface area, which aids in decomposition.”

If the final look of your garden bed important to you, it might be worth it to purchase an eye-pleasing mulch, but if you’re looking for a mulch that’s strictly utilitarian, making it yourself might make more economic sense. Here are some mulches Rick Durham, an extension specialist at the University of Kentucky, recommends using from around your farm:

Grass clippings: Use grass free of herbicides, and use newspaper underneath to prevent weeds.

Use grass free of herbicides, and use newspaper underneath to prevent weeds. Leaves or dried branches

Straw: Use newspaper underneath to prevent weeds.

Use newspaper underneath to prevent weeds. Compost: Work it into the soil slightly to promote water flow and aeration.

Making Your Mulch Decision

The type of mulch you decide to use will depend on your garden needs. For example, mulching with pine needles is appropriate around acidic plants while using a mulch high in carbon, like straw or sawdust, can be used to help balance high nitrogen levels in the soil. However, don’t confuse mulches with soil amendments, Polomski warns.

“As mulches, [the materials are] applied to the soil surface and not mixed into the soil,” he says. “When you begin mixing organic materials into the soil, you run the risk of creating nitrogen deficiencies (a “nitrogen drain”) when the carbon-to-nitrogen ratio is very high (very high carbon-containing materials relative to nitrogen).”

Be aware that some mulching materials, such as redwood or cedar mulch, could be phytotoxic to plants, and most people avoid using these around their vegetables. Also, some materials, like grass and straw, are more prone to harboring insects, diseases or weed seeds.

“People often lay a few layers of newspaper on the soil surface before they spread clippings to help prevent weed germination,” Durham says.

Keep in mind that the quality of your mulch can depend on your source, so experiment and find out what works best for your garden. Use the infographic below to learn more information about mulch and proper mulch-application techniques.

Click for larger view.



Click for larger view.