Managing Your Manure – Making Compost

One horse produces 50 pounds of manure per day. Manure and bedding for a horse in a single year can exceed 25 cubic yards. When multiplied by a number of animals, this can create a very large pile in a short time. Managing this pile can be quite the task!

Having a manure management plan can make the difference between viewing this accumulation as a big pile of waste and a headache OR an inexpensive and nutrient rich soil amendment.

A Few Options:

Cover It!	Tarp piles in winter to prevent nutrients leaching through the pile due to rainfall. Lost nutrients = pollution
Compost It!	Compost methods include aerated, windrow, static pile, turned pile, etc. Final product is a safe, stable, slow-release soil amendment. Your local SWCD can advise!
Spread It!	Generally, a 1/4" application of manure of compost can be spread once or twice annually (avoiding the wet season). Each acre treated will utilize about 33 cubic yards of material per 1/4" application.
Export It!	In no plan is made to safely utilize the manure, it may be hauled to a landfill which is expensive. Composted manure may be sold or shared. Finding a reliable taker of the product may require some searching an relationship development.

The Scoop on Compost

Composting can reduce pile volume between 30 to 70% depending on what is being composted. This reduction is based on:

• volume of materials
• size of materials
• moisture content
• bulk density
• carbon to nitrogen ratio

To compost manure fully, your pile must achieve temperatures of over 130° F. The National Organic Program recommends exceeding 131° F for 15 days and turning the pile at least five times. These temperatures will kill weed seeds and pathogens.

Regular turning or aeration will cause an active or thermal phase of composting dominated by soil bacteria that will last 1-2 months. Then, when the pile begins to cool off, the curing phase begins and continues for an additional 1-4 months. This allows time for fungi to colonize and develop a rich soil amendment.

Without turning or aeration, the composting process will take longer – up to a year or more. Also, the pile may not reach the required temperatures to kill weed seeds and parasites.

Getting the Ratio Right

The ideal environment for successful composting requires two things. The pile needs a 50% moisture content (like a wrung out sponge) and a ratio of 30:1 Carbon (browns) to Nitrogen (greens). Manure is considered the nitrogen source and bedding (straw, wood) is the carbon source.

Horse manure is excreted at nearly this ideal ratio, so it is important to minimize extra carbon from bedding. The addition of excess wood shavings increases the carbon source and slows the composting process. It may also lock up nutrients in the soil if the manure is directly applied to the field.

Adding a high nitrogen source can counter the high carbon when composting or before spreading compost with excess wood shavings. High sources of nitrogen include blood meal, bone meal, or straight nitrogen fertilizer.

Tips on Bedding and Cleaning

Consider using smaller bedding particles as they will break down and compost quicker. Evidence suggests that straw, rice hulls, and shredded paper compost ten times faster than wood shavings! Be aware that large wood chips are difficult to compost.

Try to separate out as much clean or minimally contaminated bedding as possible for other uses such as mulch, trails, or stockpiles for future composting. Using stall mats greatly reduces the need for bedding. You only need to use bedding in areas that animals use for waste.

Be selective in your stall cleaning. Only the soiled bedding needs to be removed and composted. Often, entire stalls are completely cleaned out and replaced with fresh bedding, even when much of the bedding removed is uncontaminated. Selective cleaning results in less waste to compost!

Make Compost to Use, Share, or Sell

Compost can be a great resource for use on your own land, or for export as a soil amendment to neighbors, gardeners, or farmers. Retail sale as a soil amendment may be possible, but often requires a certification. Soil amendments and fertilizers must be registered before they may be sold commercially. For more information, check out this website.

Beware of Herbicide Residue in Compost

To improve the quality of your manure or compost, consider what goes into the animal before it comes out as manure. Document all herbicide use in pastures, hay sources, and medications to make sure they aren’t reducing the value of your compost.

Certain broadleaf weed herbicides (for example those containing picloram, aminopyrilid, clorpyrilid) can persist in dry hay for up to three years. It can also persist in compost for an extended time. This means that the herbicide can still be active, even after it has been digested AND composted. If these chemicals have been used, your compost should only be used on your own grass fields, not exported. Excess livestock medications that persist in compost can also be a concern for some organic growers or food producers.

Ask Questions

Protect yourself! As a consumer, ask questions about the products you are purchasing. Also consider certifications. Yes, you may pay more, but you will also know more about the product when buying animal feeds, wood products, compost, and soil amendments (Weed Free Forage, OMRI, Sustainable Forestry, etc.). The Oregon Department of Agriculture (ODA) maintains a weed free forage certification program that is becoming increasingly popular for both buyers and sellers.

For technical assistance, please contact Clackamas Soil and Water Conservation District at 503-210-6000 or send a message to info@conservationdistrict.org .