Not all compost is created equal

On a recent sunny afternoon, I was talking with Niwot resident Alicia Livitt about compost for her garden. She was explaining that she would like a compost pile, but didn't really see where one would fit in her landscape and as an amateur gardener, the whole idea of it seems intimidating. This is an understandable and common sentiment.

In the October 2020 article Home Composting by Sharon Bokan, she breaks down how to compost your own yard and garden waste in easy to follow steps. For anyone interested in getting started yourself, I highly recommend looking it up. There is another option for getting compost for your yard and garden and that is ordering it commercially. You can buy it bagged from nurseries and garden centers or in bulk (loose) from local material yards.

The most common types available for purchase are plant-based and animal (manure) based. Plant-based compost is made up of things like leaves, grass, ground tree limbs, certain food scraps and sometimes brewery residuals. Manure based will likely include some of the bedding material that the manure was collected in. It is important to know that in Colorado there are no regulations on compost to say what goes into it or in what stage of decomposition it is.

Ideally, whatever you choose will be finished or mature compost. It should be dark and crumbly with a nice earthy smell. If it resembles the original contents, it probably isn't fully processed. The issue with using unfinished compost is that it could be "hot", meaning it has a high level of ammonia which may burn your plants.

You can use uncomposted, fresh manure, however it will also likely have high levels of ammonia and manure (fresh or aged) also has high levels of salts. To avoid the high ammonia, you can look for aged manure which is typically available bagged at garden centers and nurseries.

Aged manure will not have as strong an odor as fresh which is a bonus. It's harder to avoid the salts and therefore important to not apply too much at a time. If you suspect high ammonia or salt levels, your best bet is to work it into the soil in the fall and wait to plant until spring. The time and precipitation will help dilute the residuals.

I spoke with landscape designer Shanti Schultz of Love in Bloom and asked if she prefers plant or manure-based compost for her projects. She said that for vegetables, fruit trees and lawns she likes to use manure, and for ornamental beds she prefers plant based. When asked why, she responded, "Veggies, fruit and lawns take up a lot of nutrients, so they need the extra boost, and the nutrients in manure dissipate over a longer period of time." Whichever type of compost you choose, it should be well worked into the top 6-8" of your soil.

An important benefit of compost is that it increases the soil's organic matter. When gardeners refer to "organic matter," they are talking about organic compounds from plants or animals that are in various stages of decomposition. Colorado soils are typically low in organic matter, so unless you are only growing native plants and those which are adapted to our native soils, amending is often needed.

One way to know if you need to amend is by doing a soil test. This test gives you baseline information to work from ,and you can retest every five years or so.

For detailed instruction on how to do a soil test visit the Soil, Water and Plant Lab at Colorado State University https://soiltestinglab.agsci.colostate.edu/. For more information on compost including application rates, check out the CO Master Gardener Garden Notes #242 and #243 and #246.