Q. I have access to a supply of horse manure. Can I use it to fertilize my garden?
Fresh manure should not be used directly on plants as it may lead to burning. Well-aged manure that has been allowed to dry out can be used safely. However, dry manure is not an ideal fertilizer because it may contain weed seeds. It is better to compost the manure before using it.
The procedure for composting horse manure is no different from composting plant material. In the simplest method, a free-standing pile (say 3-4 feet square) is constructed. The pile should be kept moist and turned over regularly. Covering the pile with a tarp is a good idea, as it will help keep it moist and not too dry and will help maintain the heat. Getting the pile to heat up is important because the heat will help kill seeds and pests. Plant material can be added to the manure, but this is not necessary. The manure will probably contain bedding material (e. g. straw); this material should be kept to a minimum as too much bedding material will prevent the pile from heating up.
If the compost pile has a bad odor, it is probably not receiving enough air. If it doesn't heat up, the pile is too small or contains too much straw or other carbon-rich material.
A more efficient composting procedure is to use 2 or 3 wooden or wire mesh bins. Add manure to the first bin and treat as described above. When this bin is full, start filling the next bin. While you fill the second bin, the first bin can finish composting.
The composting process takes 2-3 months, sometimes longer. The compost is ready to use when it is dark brown, crumbly and has an earthy smell.
King County (WA) has a useful brochure on composting horse manure. It is written for stable owners but has information that any gardener can use. Also see the University of Illinois's information page.
Note that any animal manure can be composted by the same method. Chicken manure is particularly good as it is richer in nutrients than horse manure, although is more solid in texture and more difficult to handle.
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service
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