Will Horse Manure Burn My Vegetable Plants?

Green Horse Manure

• Fresh or "green" horse manure is straight from the horse, typically soaked in urine, and contains the highest levels of ammonia. Placing fresh horse manure around vegetable plants does not have the desired affect of fertilization; rather, the plants typically die in short order. In addition, green horse manure can contain pathogens and bacteria that has traveled through the horse's digestive system, as well as weed seeds. Fresh manure can contain an odor and atract flies, making it an unpleasant addition to a yard.

Composted Manure

• Allowing horse manure to compost -- or break down -- for at least six months to one year rids the compound of excessive nitrogen, prohibiting plant "burn" from high ammonia levels. In addition, the heat created as the manure decomposes kills any seeds from unwanted weeds, as well as parasites and any pathogens in the horse's system. Odors are eliminated, which should also eliminate any fly problem. Any water runoff should also be clear of contamination before it hits a groundwater source.

Manure Tea

• Making a liquid fertilizer with composted manure can provide plants with an additional layer of protection from excess nitrogen. To make the "tea", fill a bucket one-third full of aged horse manure, and fill the remaining two-thirds with water. Place a lid over the fluid, and allow the tea to "steep" or ferment for at least two weeks. Add 1 part liquid fertilizer to 10 parts water, and use it around the base of garden vegetable plants. Additional water can be added to the fertilizer in the bucket to brew additional liquid fertilizer.

Manure Comparisons

• Fertilizers such as manure are measured by the amount of nitrogen (N), phosphoric acid (P) and potash (K) they contain. Poultry manure is the richest in all three, and while horse manure only contains half the nutrients, it is still higher in nitrogen than cow manure. Both chicken and horse manures are considered "hot," however, requiring composting for safety and elimination of weeds.