Q: What is the difference between mulch and a soil amendment?
A: Mulch is material placed on the surface of the soil to control weeds, conserve moisture and reduce soil temperature. It affecst micro-organism activity.
Organic mulches include wood and bark chips, straw, grass clippings and seed hulls. Inorganic, or inert mulches, include weed-barrier fabrics, gravel and rock.
A soil amendment is any material mixed into the soil to improve such physical properties as water retention, permeability, water infiltration, drainage, aeration and structure. The goal is a better environment for roots and to improve soil fertility.
To increase moisture and nutrients in sandy soils, use well-
decomposed organic amendments, such as composts or aged manures. Improve clay soil by adding sphagnum peat, wood chips, tree bark or straw. Do not add sand to clay soil, which will create a soil structure similar to concrete.
which approach you use where. In an established garden with shrubbery and perennial flowerbeds, it is impractical to consider a soil amendment. On the other hand, if the garden in question consists ofBut with vegetables or annual bedding plants, a soil amendment can be worked in 6 to 12 inches.
Both approaches help improve soil fertility by providing organic matter for micro-organisms, insects and worms to feed on, which in turn produces nutrients plants can use.
Don t use mulch that is too fine, such as sawdust, because it will matt and prevent water from running through. If you use grass clippings, be sure weed killer wasn t used on the lawn. Don t put down more than a 1/4-inch, and allow previous layers to dry before adding more.
of soil using mulch. And, if you do amend the soil, you will most likely mulch it, as well, just for the benefits.
For more information, contact the Colorado State University Cooperative Extension office in your county and ask for Fact Sheet 7.214, Mulches for Home Grounds, and 7.235, Choosing a Soil Amendment.
Rich Himmel is a Colorado State University Cooperative Extension master gardener in Adams County.
