Can You Compost Horse Manure?
Yes, with care. Horse manure is well balanced, roughly 25–30:1 C:N, higher with bedding. The risks are weed seeds and persistent herbicides like aminopyralid from treated hay, which survive composting. Ask the stable what the horses were fed.
At a glance
| Home compost pile | With care |
|---|---|
| Green or brown | Green (nitrogen-rich) |
| Carbon to nitrogen | about 25–30:1 (approximate) |
| Moisture | Wet |
| Prep | None needed |
| Worm bin | With care |
| Bokashi | No |
How to compost horse manure
Ask the supplier whether their hay or pasture was treated with aminopyralid, clopyralid or picloram. Add manure with its bedding, and balance heavy wood shavings with extra greens. Hot composting at about 131°F (55°C) for several days, with turning, kills most weed seeds.
Many stables give manure away for free. If you can't confirm its herbicide history, use it on lawns or ornamentals, not vegetable beds.
What goes wrong
Herbicide-contaminated manure produces curled, twisted leaves on tomatoes, beans, peas and potatoes, and composting doesn't fix it. Test a batch with a simple pot bioassay, sowing peas or beans in it, before spreading it widely. Fresh manure spread on beds can also sprout a crop of weeds.
Worm bins and bokashi
Worm bin: Aged horse manure is a classic worm food, but only use manure you're confident is free of herbicides and recent dewormer residue.
Bokashi: Horse manure doesn't belong in bokashi.
This counts as a green. Adding a lot of it? Check the balance with the compost mix calculator.
From hopcompost.com/can-you-compost/horse-manure/ · General guidance, not professional advice.
Frequently asked questions
How long should horse manure age before use?
Hot-composted manure can be ready in a few months; cold-aged manure usually needs 6 months or more. Well-rotted manure smells earthy and looks dark and crumbly.
What is aminopyralid and why does it matter?
It's a persistent herbicide used on pasture and hay fields. It passes through horses and survives composting, and even small amounts can damage sensitive vegetables.
Can you use horse manure with wood shavings?
Yes, but shavings add a lot of carbon. Mix in greens like grass clippings, or age it longer before use.