Here are the results of cleaning operations on 06/03/18. Exhibit 1, from a corral containing three horses, 24 hours since last cleaning:
Next, Exhibit 2, from a corral also containing three horses, 24 hours since last cleaning:
Both wheelbarrows hold ten cubic feet. Some days you have a bit more, some days you have a bit less. Based on these results, your average horse generates about three cubic feet of waste materials per day (poop and uneaten hay).
After a few years, you’ll have quite a pile. You’re going to need a tractor to work it.
Don’t forget spare rakes and/or rake heads. A rake with one or more missing tines is a productivity killer when you’re scooping poop, but can be used well enough in the barn for cleaning up spilled hay.
Rakes with metal handles, seen in the second photo, are fine in the summer but they draw the heat out of your hands in the winter. Wood is better.
Western Horse Watchers Association 