How to Use Horse Manure as Fertilizer Safely

Turn horse manure into valuable fertilizer for your garden.

If you have horses, you've got an endless supply of free, high-quality manure compost for your garden. Most horse owners just pile manure in a corner and wait for it to decompose. By actively composting horse manure, though, you'll kill fly eggs, parasites and pathogens, making manure compost safer for garden use. You'll also reduce odors and improve the quality of the compost as fertilizer. If you are buying horse manure compost from a garden center or neighbor with horses, make sure the compost is thoroughly decomposed to kill all pathogens.

Things You'll Need

• 2 5-foot lengths PVC pipe, 2 inches in diameter
• Electric drill
• Hose
• Shovel
• Compost thermometer

Instructions

Making Manure Compost

1. Build a manure pile at least 3 feet tall. According to the Washington State University Extension Service, building a manure pile at least this high ensures that temperatures in the pile will reach a level high enough to kill pathogens and bacteria. Situate it on a level, well-draining spot that is close to the paddocks and a water source.

2. Add a small amount of bedding straw, grass clippings or sawdust to the manure. Avoid adding yard waste that's been treated with herbicides as the herbicides will survive the composting process and may later damage garden plants.

3. Drill 1/2-inch holes at 6-inch intervals in the PVC pipe. Insert the pipes in the middle of the compost pile to provide air. Aerating compost helps it break down faster.

4. Insert a compost thermometer in the center of the pile. The compost's temperature will rise within the first two weeks, then stabilize. The ideal stabilized temperature is between 135 and 150 degrees F. If the compost temperature rises above that, add water to cool it. If the compost temperature is too low, turn the compost. Adding air invigorates the decomposition process, increasing the temperature.

5. Water the compost to keep it about as moist as a wrung-out sponge. Turn it with a shovel every two weeks and check the moisture level by squeezing the compost. Water it with a hose if it is dry and crumbly. If compost is too wet, turn it to add air.

Using Manure as Fertilizer Safely

1. Buy and use only well-decomposed manure for fertilizer. It should have little or no odor and look like black soil. This ensures that pathogens are destroyed and the manure won't burn plants.

2. Check the label to ensure the fertilizer contains only horse manure. Don't use manure fertilizer that contains municipal sludge or industrial by-products as these products may contain heavy metals and harmful contaminants.

3. Spread the compost on your garden area in the fall. This will allow the horse manure to decompose thoroughly before you plant vegetables. Fresh manure can burn plants' roots and leaves. Applying fertilizer in the fall minimizes this risk.

Tips & Warnings

• If you have a tractor, use it to turn the compost pile every two weeks, rather than inserting PVC pipes into the pile.

• Limit the amount of bedding you put in compost as it will slow down the composting process. Consider using rubber mats instead of straw and sawdust for bedding.

• Manure typically decomposes in 1 to 2 months during the summer, 3 to 6 months in the winter.

• Cover compost with a tarp during wet weather.

• Don't use manure compost to fertilize vegetable gardens if you, or someone in your household, has a compromised immune system, cancer or HIV.

References

• Washington State University Extension: The Benefits of Composting
• Washington State University Extension Office: A guide to Composting Horse Manure
• Southeast Farm Press: Municipal Waste for Fertilizer Can Be Risky
• "The Garden Primer"; Barbara Damrosch; 1988

Resources

• Fine Gardening: Fertilizing the Old Fashioned Way With Manure