Ask veteran gardeners what their favorite compost ingredient is and they'll most likely tell you livestock manure. Whether it's from goats, cows or horses, animal manure provides a prime nitrogen-rich ingredient for your compost pile--and it's usually available in large quantities at farms and ranches. According to Pierce Conservation District, one horse typically produces as much as 50 pounds of manure waste in a single day. (see reference 1) But before you start tossing horse manure onto your compost heap, take a bit of time to prepare it for the composting process. Not only will the mature compost be ready more quickly, but you'll also be less likely to experience problems during the composting process.
Collect horse manure in a heap at your compost site. Gather it from your own horse stalls, scooping up as little bedding as possible when you remove the droppings. Talk to neighbors or friends who have horses, to see if they would be willing to share their manure with you. Be prepared to gather and load the manure yourself, especially if you're interested in getting it at no cost.
Sift through the pile of horse manure with a manure fork. Scoop out large pieces of the manure and lay them flat on the ground. Push the cutting edge of a shovel down through the center of each manure clump, breaking it in half. Repeat this entire process with each large piece of manure until each one measures no more than about 2 inches in diameter.
Note the amount of bedding present in your horse manure. Avoid having the bedding make up more that one-fourth the volume of your compost materials to keep the composting process from slowing down. Scoop out any extra bedding and place it to the side for use in a future compost heap. Mix the remaining bedding thoroughly with the horse manure.
Spread a 3- to 4-inch layer of mixed horse manure and bedding across the bare ground in a 5-foot-by-5-foot area. Dampen the horse manure with a light misting of water from a garden hose. Sprinkle a second 3- to 4-inch layer of the horse manure waste across the base layer, hosing it down, as well. Repeat this layering and moistening process until your horse manure compost heap measures at least 3 to 5 feet tall.