Typical N.P.K. analysis is 0.7. 0.3. 0.6
Horse manure fertilizer, like cow manure, it is one of the best soil conditioners available, due mostly to the large amount of organic matter being applied.
The nutrient value is relatively small and depends largely on factors like, the type of bedding material, if any, the food source and type, age and condition of the animal and the handling and storage of the manure. Just the same as with other animal manure fertilizers all these factors will have a big impact on the nutrient content.
Manure will decompose on its own just by piling it up and allowing it to break down until it is no longer recognizable. However composting speeds up this natural process and makes a far better product. Manure from stabled horses is going to have some bedding material incorporated anyway and is often enough on its own.
Speeding up the process and making top quality horse compost is done by layering the manure with grass clippings or a high nitrogen material, and turning or aerated it regularly to keep the heat process going as long as possible until the pile will no longer heat up.
If done properly, composting kills parasitic eggs and larvae and destroys weed seeds. The end product of composting is a dark, crumbly soil with a fresh, earthy smell.
Composting manure will take a little longer than applying directly to the garden but it is worth the extra time. Once it is done it becomes horse manure garden fertilizer and can be applied the same as compost made from more traditional materials. Spread your manure compost liberally on the garden, 1 to 4 inches (2-10 cm) thick and lightly dig it in a week or two before planting.
Remembering that compost alone from most sources will seldom supply enough nutrients for the average vegetable crop and is usually in addition to your regular fertilizer program. The main benefit of composted manure lies in the quality of organic material it adds to the soil for the soil bacteria to convert into plant usable nutrients.
Producing a good soil drenching liquid fertilizer from composted horse manure is the same as other manures. As mentioned before it is not overly high in any nutrients but the water soluble ones will be readily available to your growing plants.
Fill your container with chlorine free water. Allow enough room for the amount of compost and a little room to stir without overflowing the container.
Add the composted manure, it can be placed in a burlap sack, if you are going to use spray equipment or even a watering can. Or shovel it straight into the container if you just going to apply the finished product to the garden by bucket. Be generous with the amount you use, composted manure is not high octane stuff.
Let it brew for a week or two and apply to the garden. Don't mess around with a cup or two per plant, give them a good old drink. The residue from the brewing is still good organic matter that can be used anywhere in the garden.