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How To Compost Horse Manure For Your Garden

Horse manure is one of those amendments to a garden that really kicks it off and charges it up. Horse manure, like rabbit manure, is something I apply to my garden and compost heap pretty much every single year. For rabbit manure, I have my own source. This is another story though. Rabbit manure is a cold manure, meaning it can go directly into your garden without composting.

Horse manure, on the other hand, is a hot manure that needs to be composted before applied directly to your garden. In this article, we’ll talk about what’s in it, how to compost it, and how to use it in your garden.

What’s in horse manure?

Horse manure is an excellent addition to your compost heap. It is considered more nutrient dense than cow manure. It’s a good source of nitrogen, phosphorus, and potassium. It also contains nutrients like magnesium, calcium, and sodium, which are also important for healthy soil and robust gardens. If you grow plants that leech a good amount of these nutrients from the soil, it’s not a bad idea to add some composted manure to your garden before planting again. This will help ensure that the nutrients return to the soil and your garden will grow well.

Is horse manure dangerous?

Horse manure, if properly composted, is not dangerous. However, it can contain zoonotic pathogens like Salmonella, Campylobacter, Listeria monocytogenes, Giardia, Cryptosporidia, and Escherichia coli. These pathogens are potentially dangerous to human beings, which means you should handle it very carefully and compost it before using it in your garden. The process of composting does kill the above listed pathogens.

How to compost horse manure

Composting manure is as simple or as complicated as you want it to be. All it takes to compost manure is to put it somewhere outdoors and wait for it to compost. If I wind up with a heap of raw manure, typically what I’ll do is mix in some table scraps and maybe some chicken manure and then allow it to sit in its own heap, turning about every 2 weeks and watering during our hot, dry Oregon summers.

If possible, I like to compost it over the winter. In my neck of the woods, it rains relentlessly during our fairly temperate winters which makes for easy composting.

How long does it take to compost horse manure?

The length of time it takes to compost horse manure depends on what time of year you’re composting it and what your climate is like. In Oregon, where we have cool, wet winters and warm, dry summers, it takes about three months for it to break down, maybe a bit longer in the summer. The general rule of thumb is to allow it to sit for 3-4 months before applying to your garden.

Applying horse manure directly

Applying horse manure directly to your garden without first composting it carries dangers both to your plants and to you. It can burn your plants if applied directly in your garden and the pathogens can cause you to become ill. However, if allowed to sit in your garden overwinter, that should be ample time for it to break down and lose its potentially dangerous characteristics.

A good time to apply it to your garden is after your fall cleanup. This manure will need to sit for 3-4 months in order to be safe for you and your garden, so provided you have a winter at least that long, you should be set for applying it directly to your garden.

Where to buy horse manure

Horse manure can be purchased pre-composted and ready for your garden from many big box home and gardening stores, but I generally advise against this practice, mostly for environmental reason. The manure comes in plastic bags that are difficult or impossible to recycle and is sourced from sometimes far away places, making its carbon footprint a little too large for my own personal comfort levels.

My recommendation is to call local farms and ask if there is an excess that you can take off their hands. Most consider any amount of manure to be excess manure. Some may charge you a small fee per pound or bucket, but you’ll find that many will be eager for you to take it away and won’t charge you a dime for it. Free, locally sourced horse manure is the best manure if you want my opinion.

Thomas Nelson
Environmental Advocate
Thomas is an environmental advocate currently residing in the Pacific Northwest. In his spare time, he enjoys experiencing the outdoors, raising chickens and ducks, and reading about current environmental issues. Despite slight colorblindness, his favorite color is green.