Horse manure composts in 4 to 12 months under typical conditions, depending on how you manage the pile
Horse manure breaks down faster than cattle or chicken manure because it contains less dense material and more microbial activity. A pile left to sit without turning will take closer to a year. A pile you turn every few weeks will finish in 4 to 6 months. Temperature, moisture, carbon content, and pile size all shift that timeline—sometimes dramatically.
The manure itself is only part of what you're composting. Horse bedding (straw, wood shavings, or sawdust) makes up half or more of what you're piling up, and that bedding is what actually takes the longest to break down. A pile of pure horse manure with no bedding will compost much faster than a pile of manure mixed with shavings.
Key Takeaways
- Horse manure mixed with straw bedding takes 4 to 12 months to compost, with turned piles finishing faster than unturned ones.
- Wood shavings or sawdust bedding slows decomposition significantly—expect 12 to 24 months if shavings make up most of your pile.
- Turning the pile every 2 to 4 weeks cuts composting time roughly in half by introducing oxygen and speeding microbial breakdown.
- A pile that reaches 130°F to 150°F internally will compost faster than a cool pile, and you can measure this with a compost thermometer.
- Finished horse manure compost looks dark brown, crumbly, and smells earthy—not like fresh manure—and you can use it on gardens and pastures.
Why horse manure composts faster than other animal manures
Horse manure has a lower density and higher carbon-to-nitrogen ratio than cattle or poultry manure, which means microbes can move through it more easily and have more food to work with. Horses also digest their feed less completely than cattle, so their manure contains more undigested plant material that microbes can break down quickly.
The bedding matters more than the manure itself. If you're composting manure from a horse stall, you're composting a mix of manure, urine, and whatever bedding was in the stall. Straw and hay break down in months. Wood shavings and sawdust can take years. If your pile is mostly shavings, you're looking at a much longer timeline than if it's mostly straw.
How turning the pile speeds up composting
Turning introduces oxygen, which the microbes breaking down the manure need to work efficiently. An unturned pile will compost, but it will do so slowly and may go anaerobic (oxygen-starved) in the center, which slows decomposition and can create odor problems.
Turning every 2 to 4 weeks keeps the pile aerobic and can cut your composting time in half. A pile turned regularly can finish in 4 to 6 months. The same pile left alone might take 10 to 12 months. You don't need special equipment—a pitchfork and willingness to move material from the outside of the pile to the center works. If you have a tractor with a bucket, that's faster, but not necessary.
If you don't turn the pile, it will still compost. You're just trading time for labor. An unturned pile of horse manure and straw will be ready in about a year. An unturned pile with shavings might take 18 to 24 months.
Temperature and pile size affect how fast decomposition happens
A larger pile heats up faster and stays hot longer, which speeds decomposition. A pile smaller than 3 feet on each side may not generate enough internal heat to compost efficiently. A pile 4 to 5 feet on each side will heat up to 130°F to 150°F internally within a few days if the conditions are right, and that heat accelerates microbial activity.
You can measure internal temperature with a compost thermometer (a long probe thermometer, about $15 to $30). If your pile is staying cool, it's either too small, too dry, or too carbon-heavy. Adding more manure, water, or nitrogen-rich material (grass clippings, kitchen scraps) can raise the temperature.
Ambient temperature also matters. A pile built in spring or early summer will compost faster than one built in late fall or winter, because the surrounding air temperature helps maintain the internal heat. A winter pile will still compost, but more slowly.
Moisture balance keeps decomposition moving
The pile should feel like a wrung-out sponge—damp but not waterlogged. If it's too dry, microbes slow down. If it's too wet, it becomes anaerobic and smells. Horse manure with straw bedding usually has enough moisture from the urine in the manure, but if you're adding dry material or live in a dry climate, you may need to water the pile.
If the pile smells like ammonia or rotten eggs, it's too wet or too nitrogen-heavy. Turn it more often or add dry carbon material (leaves, straw, wood chips). If it's not heating up and feels dry to the touch, add water when you turn it.
Recognizing finished compost and when to use it
Finished horse manure compost is dark brown or black, crumbly, and smells earthy—not like manure. You should not be able to identify the original bedding or manure. If you can still see straw or wood chips, it's not finished yet.
You can use finished horse manure compost on vegetable gardens, flower beds, pastures, and lawns. It adds organic matter and nutrients to soil. If you're using it on a vegetable garden, let it finish completely before explore it—partially decomposed manure can burn plants and may harbor pathogens.
If you're composting manure from horses treated with dewormers or other medications, those chemicals can persist through composting. If this is a concern, research the specific medication or compost the manure separately and use it only on ornamental plants or pastures, not on vegetable gardens.
Wood shavings and sawdust bedding extend composting time significantly
If your horse bedding is wood shavings or sawdust, expect composting to take much longer than with straw. Wood is high in carbon and low in nitrogen, and it breaks down slowly. A pile that is 50% shavings by volume might take 18 to 24 months to compost, even if turned regularly.
You can speed this up by mixing in nitrogen-rich material—grass clippings, kitchen scraps, or additional manure from other animals. You can also separate the shavings from the manure before composting. Some people compost shavings separately from manure, or use shavings in a separate pile with added nitrogen sources.
If you have a choice of bedding and plan to compost, straw or hay is significantly faster than wood products. If you're already using shavings, accept the longer timeline or plan to compost it in a dedicated area where it can sit undisturbed for a year or more.
Frequently Asked Questions
Can I use horse manure directly on my garden without composting it first?
Fresh horse manure can burn plants because of its high nitrogen content and heat generation. It's safer to compost it first. If you must use fresh manure, explore it in fall for spring planting so it has months to break down in the soil, or use it only on ornamental plants and lawns, not vegetables.
Does a covered pile compost faster or slower than an open one?
A covered pile retains moisture and heat, which can speed composting slightly. However, it also reduces airflow if not designed with ventilation. An open pile that you turn regularly will compost just as fast or faster. A cover is useful mainly to keep rain from waterlogging the pile or to contain odor.
What if my pile smells bad?
Ammonia or rotten-egg smell means the pile is too wet, too nitrogen-heavy, or anaerobic. Turn it more often, add dry carbon material like leaves or straw, or let it dry out slightly. If it smells like manure but not foul, that's normal and will fade as it composts.
Can I add other materials to speed up horse manure composting?
Yes. Adding grass clippings, kitchen scraps, or leaves adds nitrogen and microbes that speed decomposition. Avoid meat, dairy, and oils. Grass clippings are particularly useful because they're nitrogen-rich and break down quickly, which heats the pile and accelerates the whole process.
How do I know if my pile is finished composting?
Finished compost is dark, crumbly, and earthy-smelling. You should not see the original bedding or manure. If you're unsure, wait another month and check again. It's better to compost too long than too short—partially finished compost can still heat up in soil and damage plants.