A Guide to Composting Horse Manure

by Jessica Paige, WSU Cooperative Extension, Whatcom County

Back to Composting Methods

Compost Troubleshooting Guide

Condition or SItuation

Possible source or reason

Other Clues


Pile fails to heat

Pile to dry

Cannot squeeze water from material

Add water/wet the pilce


Material to wet

Materials look or feel soggy, pile slumps

Tund and/or cover pile


Not enough nitrogen

Large amount of bedding

Add high nitrogen ingredients, reduce bedding


small pile size

Pile height less than 3 feet

Enlarge or combine piles.

Temperature falls consistently over several days

Low oxygen

Temperature declines gradually rather than sharply

Turn and/or cover pile


Low moisture

Cannot squeeze water from material

Add water


Materials too wet, insufficient aeration.

Low temperatures

Turn pile, add PVC pipes, cover

Fly problem

Flies breeding in uncomposted manure


Cover pile with a tarp or a 6-inch layer of finished compost to prevent access.


How to Know When Compost Is Ready for Use

The composting process begins as soon as you begin to pile up your manure. Almost immediately, microorganisms begin their work and temperature increases are often noticeable within a few hours of forming the pile. With adequate airflow and moisture the pile's temperature should increase rapidly to 120F-160F and may remain in this range for several weeks. As active composting slows, temperatures gradually drop to around 100F and then to ambient air temperature. Compost should "cure" for at least a couple of weeks before use. Finished compost is a crumbly, evenly textured, earthy-smelling, dark material that looks like a commercial potting soil mixture. It will probably take about one to three months for each pile to compost during the summer and about three to six months in the winter. If you monitor your piles with a thermometer you will see a gradual drop in the higher "active" composting temperatures as it begins the curing process and becomes ready for use.


What to Do With Your Finished Compost

Spreading compost on pastures. The easiest way to spread compost is to use a manure spreader and a tractor (or a strong riding lawnmower) to load, pull, and spread your compost. But you can also spread it without all that equipment: all you need is two people, a shovel, and a riding lawnmower, small cart, or pickup truck. Simply have one person drive while the other person spreads a thin layer of compost.

Only spread compost during the growing season (April-September) when plants can use it and when it's less likely to be washed away by the rain. Apply approximately inch at a time (you don't want to smother the grass) and no more than three to four applications per year. Re-apply only after the previous layer has worked its way into the soil.

Using compost in garden and landscape areas. Compost can be worked into garden beds by hand or with a tiller or added to the soil when planting trees, shrubs, annuals, or perennials. Compost is also an excellent mulch or topdressing around flowers, shrubs, and trees. This mulch will help your plants get through the dry summer with less need for irrigation. When using it as a mulch around trees or shrubs, start three to four inches from the trunk and spread the compost out to the dripline keeping it about three inches deep.

Selling your compost. To find a buyer for your composted manure, contact local topsoil companies, tree farms, landscapers, and organic farmers. There's a good chance that you will need to deliver it to them but you can still end up making a profit on your compost.

Giving away your compost. If you somehow end up with compost that you want to get rid of, post a "free manure compost" sign where people can see it from the road. Try to make your pile easily accessible so that people can simply drive up and take what they want, when they want. You can also put an announcement in local newsletters and newspapers-many papers will let you advertise free things at no charge.

Compost Bin Designs


The Rodale Book of Composting. Rodale Press, Inc., 1992.

Field Guide to On-Farm Composting. Natural Resource, Agriculture, and Engineering Service, 1999.

Healthy Horses, Clean Water. Horses for Clean Water, 2000.


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