By Craig Witt and Mark O’Farrell, Soil Council |
What is the difference between mulch and compost?
Repeat this simple mantra over and over: Healthy plants need healthy soil.
A healthy soil is teaming with millions of living organisms that all contribute to the health of your plants. To get through a brutal high desert winter, your soil microbes need two things, food and shelter.
In simple terms, compost is food for your soil and mulch provides shelter. Compost is generally much finer than what you would use for mulch. It is organic matter which has been broken down by fungi and bacteria. It is usually very dark brown and smells slightly sweet, like healthy rich topsoil. If it smells sour, putrid or you detect a hint of ammonia, it means that it has not been composted properly. Avoid it like the plague.
To be a good food source, compost is applied directly to the soil where the microbes can get to it. It can be incorporated into the top few inches of soil and covered with mulch.
Mulch serves as shelter for your soil, so it always goes on the surface, after a good meal of compost. It protects your soil from extreme temperatures in both summer and winter. It also prevents erosion from wind, rain and poorly adjusted sprinkler heads.
Should I use that pretty colored rock for mulch in my landscape?
That depends on what the goal of mulching is in your particular landscape. For large open areas where your goal is low maintenance, rock is certainly a reasonable alternative. It also works well for some high traffic areas or overflow parking.
For any areas where you have plants, however, you would want to use an organic mulch like walk-on bark or wood mulch. Organic mulches serve the primary purpose of suppressing weeds as well as, or better, than rock mulches. In addition, they provide two major benefits to your landscape that rock mulches do not.
Organic mulches are usually less dense, so they provide a greater R-value in insulating your soil from temperature extremes. Organic mulches also improve your soil over time as they are broken down by microbes, contributing valuable organic matter to the soil.
An interesting fact about redwood bark mulches or “Gorilla hair” mulches is to understand that redwood resists decomposition in the soil. That’s the reason that many fence posts and containers are made out of redwood. They last longer before decomposing. Sometimes this can be an advantage, but it is a disadvantage for increasing your soil’s fertility. Many mulches, if they are not composted, can have phytotoxic characteristics. That means they actually inhibit plant growth. Two good examples are Walnut and
Eucalyptus. It’s best to know where your mulch comes from and what it is made of. For more detailed information on mulches, see www.attra.org.
For more info, contact Craig Witt and Mark O’Farrell at Full Circle Compost at (775) 267-5305 or craig@fullcirclecompost.com or mark@fullcirclecompost.com.
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