One horse creates about 50 pounds of manure a day. That’s 9 tons every year, enough to fill 27 raised beds measuring 8 feet x 4 feet – each a foot deep! HOLY COW!
Horse manure is lightweight, rich in nitrogen (more than cow manure) and does a great job of loosening clay soils. To get the healthiest manure possible, find out if herbicides are used on the meadows where the horses graze and if the animals are given antibiotics or other medications. If so, seek out an alternate source of horse manure.
The safest way to use horse manure fresh is to incorporate it into the soil in the fall and let the snow cover and cold temperatures naturally blend it into the soil. If you cannot let it overwinter, apply it at least 120 days before the harvest date for crops that touch the soil and 90 days for all others.
Wood shavings mixed with horse manure can rob your plants of nutrients because the microbes must take nitrogen from the soil to break the wood down. To solve that problem, compost the manure, and in the process you will also eliminate most weed seeds and pathogens. See the recipe on Composting Manures above.
Which Edible Crops Benefit from Horse Manure?
Because horse manure is low in phosphorus and potassium, it is not the best choice for flowering plants, tomatoes or peppers. Use it instead on leafy, nitrogen-needy plants such as corn, potatoes and lettuce.
Garlic seems to grow really well in soil amended with composted horse manure.
Consult the cow manure recipes above, keeping in mind that horse manure is more potent and may contain more salt.