Managing Manure

Manure is something all horse owners must deal with, but it can be worth its weight in gold as a fertilizer if properly composted.

There is no shortage of manure on a horse farm. We're simply rich with the stuff. And whether our farm is large or small, we need to have a plan for what to do with the seemingly endless supply of often-odiferous waste.

The typical 1,000-pound horse produces about 50 pounds of manure per day, or 8 to 9 tons of manure per year. Some of the options for disposal include stockpiling (for later spreading), composting, hauling it to local landfills (if allowed), or selling/giving it to people for fertilizer.

Betsy Greene, PhD, associate professor and extension equine specialist at the University of Vermont, says if you are storing or composting manure, it should be done properly. "For example, in Vermont there are AAPs (Accepted Agricultural Practices), and these can be viewed on www.vermont (search AAP)," she says. "In Vermont, manure piles can't be within 100 feet of a private well, or stacked in the field within 100 feet of any surface water, or on any land that is subject to overflow or runoff." Small acreage subdivisions might also have covenants that restrict spreading of manure.

"Often horse owners don't consider themselves farms or agriculture," says Greene. "But they are a livestock operation and fall under the same rules and responsibilities--to make sure they are following acceptable agricultural practices. Good stewardship is the key. Even if you just have five retired horses and are not a business, if you are stacking manure somewhere near your neighbor's well, this is not allowed.

"Another rule in Vermont, since we have cold winters, is that you can only spread manure on your property when ground is not frozen, otherwise it will just run off," Greene adds. "You are not allowed to spread manure between Dec. 15 and April 15. You also need to minimize runoff from any high-traffic areas, barns, and pens. You are responsible if there is any runoff into ground water after a downpour or snow melt."

For manure storage you need a concrete pad with geotextile fabric and gravel or some sort of drainage and water diversion around it, so you are not just piling manure on something that will leach it down into ground water. "Even just covering a manure pile can make a difference in how much water may run through it and cause dirty runoff," she says. "Many horse owners don't have much room, or not enough equipment to spread manure on their pasture. Their pastureland may be minimal or broken into small pieces. Most don't have the equipment needed to load and spread manure."

So horse owners need to figure out where they can store or stockpile manure, or they should partner with someone who might need it as fertilizer. "Horse bedding and manure can help make good compost," says Greene. "If a dairy farmer nearby is trying to compost, he needs organic matter to add to the cow manure. The extra straw or shavings from horse bedding adds the needed carbon to the mix for better compost. Dairy folks generally don't have the high ratio of bedding to manure, so horse manure and shavings can be a valuable component for their compost."

Some horse owners fill large bins that a compost business provides. "Earlier you got paid for horse manure," she says. "Now you generally have to pay to have the manure hauled off, but this is still better than having no way to get rid of it."


Composting involves piling manure/organic matter to optimize fermentation and microbial action that create heat and break down the material into more basic ingredients. Oxygen-dependent microbes (primarily bacteria and fungi) accomplish the decomposition process. Heat the compost pile generates kills most of the parasites, pathogenic bacteria, and weed seeds, and it eliminates most of the moisture in the material. During composting the manure pile shrinks in size and weight and turns into a dark, loamlike material with an earthy smell that isn't offensive.

Composting is the most labor-intensive method of manure management. Sandy Gagnon, extension equine specialist at Montana State University, says you need some way to turn and water compost to keep the moisture content at about 50% and the temperature at the right level. "The pile must reach 145ºF or it won't break down properly," says Gagnon. "Composting must be done correctly or the pile attracts flies and produces offensive odor. In an urban area you don't want your neighbors complaining about flies or odor.

"The area between the compost pile and any water source should be planted in some kind of grass that is durable and acts as a filter system so any runoff from the pile will be captured and not get into the water source," he adds. Don't put the pile in a low area where moisture might collect and make the piles soggy.

A good resource for proper composting techniques is The Horse Owner's Guide to Composting, by Steven Wisbaum. Greene edited this booklet, which was published in 2002. She says this reference material can be found on the University of Vermont Web site at grams/agriculture/equine/downloads/horsemanurecompost.pdf. This publication discusses the major reasons for composting (protecting water resources and equine health, improving horticulture value of manure, and reducing operating costs), the benefits of using compost, the art and science of composting, manure storage and compost area design, compost mechanics and equipment, monitoring the compost process (moisture, temperature, odor, and physical appearance), compost troubleshooting, determining when the compost is done, and application rates and methods for using it as fertilizer.

In some regions composting businesses market the product as bagged fertilizer. "In Lexington, Ky., for instance, there are large facilities where nearby horse farms send their manure and old bedding, where a tub grinder mixes all the straw and manure together, and then it's put in bins for composting," says Gagnon.

Using Manure or Compost as Fertilizer

In order to use manure as fertilizer, you need enough pasture area for rotational grazing, so the horses are not always on the same piece of land. "Common recommen- dations are that you compost manure and bedding prior to spreading it; the end product will be better for the soil and plants," says Greene. "If you have hay fields or pastures where you take the horses off in winter, or pasture you can use rotationally, you can spread compost on the areas that are not being grazed."

In a hot, dry climate fresh manure can be spread on pastures that are not being grazed. Heat and drying kill many parasite eggs and larvae. "But if you are continually grazing the pasture or live in a cool, wet climate, it is always a good idea to compost manure before spreading it to protect your horses from parasites," says Gagnon.

Compost is also healthier for pastures than fresh manure. The latter can kill the plants if spread too thickly, since the acids, salts, and ammonia are too concentrated.

You can apply composted manure once a year to pastures, preferably in early spring and no deeper than about three-quarters of an inch. A manure spreader works well, followed with a harrow if necessary to spread it more thinly and evenly. Horse manure has a different composition than cow manure, and fresh horse manure is often too rich for many plants unless mixed with straw or other organic materials or broken down as compost. It has the perfect pH, however, for roses, azaleas, evergreens, or other plants that thrive in an acidic environment. For best results as general fertilizer, however, it should be composted along with used bedding.

Composted manure contains well- balanced plant nutrients, supplying a form of nitrogen that is less likely to wash away and contaminate water sources. It also returns needed microorganisms to the soil, and this improves moisture-holding capacity. The nitrogen in manure has a more slow-release effect than that of chemical fertilizer, and it is less apt to wash away.

"Nitrogen in horse manure is about 19 pounds per ton, which is higher than cattle manure, so many people like it for gardens," says Gagnon.

If you don't have enough land on which to spread compost, contact local fruit and vegetable farmers, especially the ones who use natural fertilizer rather than commercial chemical fertilizer. "Some people sell manure or compost, or tell farmers and gardeners they can pick it up for free," says Greene. "In the Montpelier area livestock farms are partnering with organic vegetable farms to utilize compost. Often the vegetable and dairy farms have the necessary equipment to load and haul it."

Crops and vegetables use up soil nutrients as they grow and farmers need a way to replace these. Manure or compost is the best way to add important nutrients back into the soil. "Organic farmers cannot use chemical fertilizer, but can utilize manure or compost if they can be assured it contains no chemicals or pesticides," Greene says. If you use feed-through dewormers, this would negate your option for giving/selling the manure to an organic farmer. But sources say most horsemen are not feeding or injecting their horses with anything that would be a problem. There are also a lot of nonorganic farmers who do not have the strict rules to maintain their "organic farm" status.

It's also important to note that if your horses have grazed fields or eaten hay from fields that have been treated with the herbicide Grazon (containing clopyralid), your compost will be worthless as a fertilizer and could even harm the environment. Manure from horses that have eaten treated hay or grass still contains the chemical, which will persist in organic material for up to five years. It will kill all broad-leaved plants. If you're not able to find out whether your hay sources use Grazon, grow a test plot of vegetables using composted manure from your farm.

Take-Home Message

Horse manure can be a problem or a blessing for farm owners. Pile too much on the fields, and you can destroy them and cause health problems in horses. But, if handled properly, horse manure can be transformed into environmentally friendly fertilizer.

About the Author

Heather Smith Thomas

Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog,, she writes a biweekly blog at that comes out on Tuesdays.

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