CORVALLIS, Ore. — Don’t discard the manure that chickens, horses or llamas leave behind. With a little time and care, it can become one of the most valuable resources in your garden.
“Manure is a low-cost fertilizer and a wonderful way to utilize nutrients instead of creating a large pile that is not getting used and could be harmful to water quality."
“Manure is a low-cost fertilizer and a wonderful way to utilize nutrients instead of creating a large pile that is not getting used and could be harmful to water quality,” said Melissa Fery, Small Farms faculty member with the Oregon State University Extension Service and associate professor of practice in the College of Agricultural Sciences.
Livestock manure is rich in nitrogen, phosphorus, potassium and other nutrients plants need to thrive. The exact nutrient makeup depends on the animal’s diet, digestive system and the amount and type of bedding used, Fery said.
When added to soil, manure improves soil structure and increases its ability to store water — reducing the need for frequent irrigation.
Compost manure before using
Fery recommends hot composting manure before applying it to the garden. Composting kills parasites, reduces weed seeds and makes manure easier to handle.
“Hot composting balances food, water and air in a compost pile to favor microorganisms that thrive in high temperatures,” she said.
If using fresh, uncomposted manure, dig it into the soil at least 90 days before harvest to reduce the risk of foodborne illness.
“It takes at least one-half cubic yard of fresh organic matter for a compost pile to heat up and reach the recommended temperatures for hot composting,” said Nick Andrews, Extension organic vegetable specialist. “The pile should also have a balanced carbon-to-nitrogen ratio and good moisture and air.”
Build two bins for efficient composting
A simple way to start is by building two bins from pallets or boards. The first bin is for active composting; the second is for curing — the final stage of decomposition, which can take several months.
Make bins large enough to hold a pile 4 to 6 feet high and 3 to 5 feet wide. Mix fresh manure with “brown” materials such as dry leaves, straw, spoiled hay or shredded paper. If manure already contains bedding, it likely has the right balance of carbon and nitrogen. Thick layers of a single material decompose slowly, so mix thoroughly.
Check the pile’s moisture by squeezing a handful while wearing gloves. It should feel damp and release a few drops of water. Add water if it’s too dry, or mix in dry material if it’s too wet.
Turn the pile several times during the first month to provide oxygen and distribute heat. It should reach 130–140°F when conditions are right. After the pile cools to ambient temperature, move it to the second bin to cure.
Use compost safely and sparingly
Once the compost has aged for two to six months, it’s ready to use in potting soil or garden beds. Spread composted manure in a thin layer — about ½ to 1 inch deep — to enrich the soil without overloading it with nutrients.
Store compost away from water sources and cover with a tarp before heavy rain to prevent runoff. Avoid applying excessive amounts year after year, which can cause nutrient buildup and water pollution.
Horse manure mixed with sawdust or straw bedding may take longer to break down. Always wear gloves when handling raw compost and wash hands afterward.
For composting questions, contact Master Gardeners at your county’s OSU Extension office.
Learn more
For additional guidance, explore this Oregon State University Extension Service publication:
Previously titled Turn manure into compost for your garden
