Manure Management

Every barn manager and anyone who keeps his or her horses at home knows that disposing of manure and soiled bedding is a mounting problem. If allowed to accumulate, raw manure serves as a vector for parasites and other organisms, attracts flies, and, if extensively amassed, increases the risk of thrush and other hoof-related problems. After it dries, copious amounts of fecal material create a dusty, spore-laden environment that can cause respiratory distress in horses and aggravate allergies, lung problems, and eye irritations in humans. If situated incorrectly, raw manure can leach nitrates into wells, water tables, or streams, posing health risks to consumers.

Manure Management

The average horse produces about 45 pounds of manure and urine a day. That's more than eight tons of dung a year per horse!

Besides the problems caused by the manure itself, increased environmental regulations in many areas dictate how manure must be handled or stored. Several states now require that farmers prepare management plans for spreading chemicals and manure, while encroaching suburbs into rural areas demand storage solutions that aren't offensive to sensitive, countrified urbanites.

Then there's the problem of just dealing with the sheer volume itself: The average horse produces about 45 pounds of manure and urine a day. That's more than eight tons of dung a year per horse!

Fortunately, several methods address the particular needs of small, large, rural, and suburban horse farms. Some methods are inexpensive, but more labor intensive, while others require more expense, but less labor.

Simple Composting

Probably the most common and least costly method of handling manure and soiled bedding is through aerobic (oxygen-caused) composting. Says Michael A. Schmitt, PhD (agronomy), associate professor/extension soil scientist, Department of Soil, Water, and Climate, University of Minnesota, "Composting is taking a raw waste--manure--and undergoing a process that essentially heats up the manure. Heating eliminates some of the parasites and weed seeds in the manure, and drives off a good share of the water. The mass decomposes and, after the composting period, ends up as a product that doesn't look like raw manure anymore; it has an earthy smell."

When fully composted, the mass shrinks in size, weighs less, and has turned into a dark, loamy-like fertilizer.

Creating a good compost pile begins with the correct ratio of manure, bulking agent, water, and oxygen. Tom Halbach, MS (agricultural geography), State Specialist--Waste Management, University of Minnesota, says that a good compost pile needs to be at least one cubic yard or larger to obtain higher temperatures, should have about a 55% moisture content, a minimum of 5.5% oxygen throughout the pile, microorganisms, and a carbon:nitrogen (C:N) ratio of 30:1. Nitrogen is a nutrient found in the manure; carbon is an element found in the bedding material--straw, wood shavings, sawdust, etc.

Piles that are properly constructed and maintained break down the fastest--as quickly as 90 days--although the average time is closer to 120 days. Piles that don't have the correct mix or aren't maintained break down much more slowly, taking six to twelve months or more. "Even bad compost eventually turns into good compost in about four years if left alone," says professor Halbach.

Good compost begins with the optimum C:N ratio. One might have a laboratory analyze samples of the bedding and the manure, then calculate and adjust the ratio accordingly by decreasing the carbon (bedding) or adding more nitrogen. Local cooperative extension bureaus can provide information on manure testing, with challenging information for calculating C:N ratio and moisture content available at a Cornell web site at

Or, one can estimate the C:N ratio. "Typical straw has a C:N ratio of 80-100:1," says professor Halbach. "Shredded newspaper has a C:N ratio of about 170:1, sawdust from mixed hardwoods ranges from 400-600:1, and wood shavings from pine trees have a value of about 600-800:1. Horse manure and urine together are about 12-16:1." Bedding with higher C:N ratios should have additional nitrogen thrown in. "The easiest way to do that is with urea, a chemical fertilizer that has 46% nitrogen," says professor Halbach. "If you don't like math, you could put down less bedding or you could just accept the fact that it will take longer to break down. Rather than 90 days, it may take you 180 days."

Or, one can forget about C:N ratios and just play the odds. "Midwest Plans Service Inc. (1988) estimates that the average horse produces about 45 pounds of manure and straw bedding per day," professor Halbach says. "This mixture has a C:N ratio of 32:1, and a moisture content of about 69% on a wet basis. (Horse manure ranges from 50-79% moisture, with 69% about average.) This is close to the conditions we are trying to achieve."

Professor Halbach points out, however, that opinions are divided on what constitutes the "typical" C:N ratio of manure and straw bedding; Cornell University calculations for the above would yield a 48.3% moisture content and 46.6:1 C:N ratio.

A 50% moisture content is needed in the pile throughout the entire composting process. "One of the big mistakes people make is putting a lot of water on the pile at once, then ignoring the pile," professor Halbach says. Moisture can be gauged by squeezing a handful of compost. "If it feels moist to the touch, but you cannot squeeze any water out of the compost, it's about right. If you can squeeze water out, it's too wet. If it doesn't feel moist, it isn't."

Sufficient amounts of oxygen are necessary for the health of the pile. The porous, spongy consistency of straw usually provides close to the right amount of free air space within the pile, professor Halbach says. Sawdust, ground bedding, and other materials with a finer consistency pack too tightly. One can measure the oxygen in the pile with an oxygen meter (ranging from $400-$1,400) or a temperature probe. "If the temperature goes up to 120-130° Fahrenheit pretty quickly, you've probably got enough oxygen in there," professor Halbach says. Temperatures above 160 or 170° could indicate a lack of oxygen; adding a little straw could correct that.

Microorganisms that break down the compost are the final ingredient. Although they can be purchased, microorganisms already present in old manure, compost, and top soil are usually all that are needed.

After the materials are assembled into a mass, the compost pile heats up. Because the pile will be hotter at the center than the outer edges, the pile needs to be turned and mixed. The more it's turned, the faster it breaks down. "In general, four to eight turns during whatever time period you're going to be composting," professor Halbach says. "If you're composting 180 days, you might turn it three or four times the first two months, and then less often as it gets older."

Temperatures at the center should be kept between 122-150°; a temperature probe--an excellent, inexpensive investment-- eliminates the guesswork. The EPA recommends 131° F for a minimum of 21 days, turning a minimum of seven times, to reduce disease pathogens, and 150° F for at least seven days to reduce weed seeds.

Piles that are too cool--below 122° F--break down more slowly and don't reduce parasites or weed seeds. Piles that are too hot--160° F and above--begin killing the microorganisms. "By 176°, we've killed all the microorganisms," states professor Halbach. "The pile goes anaerobic and is extremely foul-smelling. If the pile gets too hot, make the pile smaller. If it gets too cold, make it bigger." Five-to six-foot depths work best.

Compost piles can be built in vertical stacks or windrows, or amassed in bins.

  • The simple vertical pile works well for one- or two-horse operations where manure and bedding are continually added to the top or sides of the mass. Frequent turning of the pile will hasten the composting process, but many prefer a less labor-intensive approach of building a new pile once or twice a year, turning the pile two or three times, then letting it take a year or so to mature.
  • Windrow composting, where manure and bedding are piled horizontally, is good for people with large herds and sufficient room. Typically the windrow is a long row six to eight feet wide, about five to six feet tall, and anywhere from a dozen feet to several hundred feet in length. These piles are usually turned with mechanized equipment, rather than by hand. "The size of these piles-- long and narrow, tall and wide--will differ, based on the type of equipment available to turn the piles," says Pat Millner, USDA research leader for the Soil Microbial Systems Laboratory, Agricultural Research Service Center, Beltsville, Md. "Some use miniature front end loaders to scoop up and turn the material over, so that the material on the outer edges of the piles gets put into the center, so it can remain in the 'hot zone' for several days. Others may use a tractor with an adapted implement that sticks out from the side while being pulled behind as it turns the pile. The tractor does not itself ride over the pile, but rather between or alongside the windrows."

Bin composting works well when smaller amounts of material need to be composted says Miller. "As you periodically add material to the bin you need to cover it with several inches of straw, old hay, or finished compost. Then you periodically turn the material with a shovel, pitch fork, or small bucket loader (if it will fit into the bin opening), to remix and promote reheating."

Bins may or may not be covered to prevent rainfall collection; larger bins, in which bucket loaders are used to move the compost, will be easier to manage with a concrete floor and a strong wall to push the compost against. Often a series of bins are used: Materials are piled into bin one until it's full, then turned into bin two for about two months, then turned into bin three for another two months. Some of the material in bin one will still be incompletely composted when turned into bin two; it will finish composting later in the other bins.

Compost sites should not reside within 100-200 feet of wells or water sources to avoid leaching during heavy rains, nor be situated where water collects. Ideally, the pile should be on a fairly flat site where one can maneuver around to turn the pile manually or with mechanized equipment, and, if possible, close to the manure source.

In populated areas, a site away from residential areas might make for happier neighbors, even though a good pile will not draw attention to itself. Says professor Halbach, "A well-managed pile does not have a foul odor; it smells the same as when frost goes out of the soil in the spring, or after a rain storm when the garden is tilled." Nor do proper piles attract flies. "Once you get those temperatures of 130-150° F in the pile, it's hot enough to kill most larva, so insects don't want to be around there."


Many folks, particularly those with a lot of land, deal with raw manure by spreading it on croplands or unused pastures. Says professor Halbach, "The advantage of direct land application of manure is you retain up to 30% more nitrogen when applied and tilled into the soil. There is greater nitrogen loss if the manure is just spread on the surface. On the downside, spreading doesn't deactivate weed seeds or aggressively attack pathogens." Egg-type parasites can live for years in the soil.

Manure should be spread uniformly and evenly, says Schmitt. "If you don't spread those piles, the ammonia and salts in the manure can become too concentrated and will kill all the grass underneath. Go out with a spike tooth harrow or a drag a couple of times a year to level those manure piles."

Opinions are divided on when horses can be turned out on spread pastures. "The general rule is that six months is enough for sunlight, temperature, and surface microbial activity to deactivate most of the pathogens to the point that it's safe for most horses," says professor Halbach.

Horses which spend most of their time in the pasture do their own spreading, tending to defecate in one area and graze in another. Says Randel Raub, PhD (animal science), of Kansas State University, "We have most of the Kansas State herd in a pasture setting. We don't overpopulate our pasture, so nature takes care of the manure problem. If your horse has enough room, manure disposal is taken care of by the elements and is not a problem." Although some suggest cleaning pastures to reduce parasite infestation, Raub points out that in adequately sized pastures, good deworming programs can yield the same protection.


In certain areas, burning manure waste can be a quick and efficient option. Place fresh manure in a drying pile that's a little spread out. After it's dried, set it on fire or add it to an already smoldering pile. "It's like starting charcoal," says Raub. "You'll have a fire initially, then it's like hot coals just burning overnight: You go out the next morning and have half or a quarter of the volume in ashes."

Zoning regulations might prohibit burning in many areas, but in places where burning is permitted, the burning site should be situated where the smoke and smell won't trouble neighbor,s and it should be set well away from pasture or dried grass where a sudden wind could spark a wildfire. "Beat the grass and foliage down so there is bare ground around the fire, and provide a windbreak for it farther back," advises Raub.


Those without the time or available land to compost, spread, or burn might have to pay commercial haulers to remove their waste. This method is the least labor-intensive, but it is also the most expensive.

Although there might be an interest by local gardeners or nurserymen for hauling away or purchasing composted manure, fresh manure has limited value to these people because the manure will heat up and burn the plants it's applied to, and can introduce additional weed seeds into a new environment. Nevertheless, sometimes such arrangements can be made. This summer, Kansas State University struck a deal with a commercial nursery whereby the nursery pays KSU to haul away loads of raw manure; the nursery uses the material to create its own mulch.

Consult with the local cooperative extension agent to locate a hauler.

About the Author

Marcia King

Marcia King is an award-winning freelance writer based in Ohio who specializes in equine, canine, and feline veterinary topics. She's schooled in hunt seat, dressage, and Western pleasure.

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