Horse Manure (0.7-0.3-0.6) - is richer in nitrogen than cattle or swine manure, so it is a "hot" manure. A common source of horse manure is rural stables, where owners usually bed the beasts very well. Horse manures sourced from stables, therefore, may also contain large amounts of other organic matter such as wood shavings or straw with manure mixed in. Some sources of mushroom compost contain large quantities of horse manure and bedding in their mix. So from one standpoint, horseshit's use in herb growing is already fairly well documented. Horseshit, because it is hot, should be composted along with other manures and higher carbon materials. Unfortunately, horse crap also contains a higher number of weed seeds than other comparable manure fertilizers.