CORVALLIS — The manure that chickens, horses, llamas and many other barnyard animals leave behind is rich in nutrients that make a great organic fertilizer for your garden, said Melissa Fery, an instructor with the Oregon State University Extension Service's small farms program.
"Manure is a low-cost fertilizer and a wonderful way to utilize nutrients instead of creating a pile that is not getting used and could be harmful to water quality," she said.
If you add animal manure to your soil, you'll not only improve the quality of the soil but you also won't need to water your garden as much.
All animal manures are good sources of nitrogen, phosphorous, potassium and other nutrients that plants need to thrive. But the amounts of each nutrient are highly variable depending on the animal's diet, and the amount and type of bedding used, Fery said.
Fery recommended hot composting manure before applying it to your garden to kill parasites and reduce seeds from weeds. Composted manure is also easier to shovel and spread. Hot composting balances food, water and air in a compost pile to favor the growth of microorganisms that thrive in high temperatures.
"It takes one-half to one cubic yard of fresh organic matter for the pile to reach the recommended temperatures for hot composting," said Nick Andrews, small farms specialist with the OSU Extension Service. "The pile should also have a balanced carbon-to-nitrogen ratio and good moisture and oxygen supplies."
A simple way to start is by building two bins out of pallets or boards. The first bin is for making the compost and the second is for the final stage of decomposition, also known as curing. Curing stabilizes the compost and can take several months. Make the bins big enough to hold a pile that could get 4- to 6-feet high and 3- to 5-feet wide.
Mix or layer raw animal manure with brown leaves, straw, spoiled hay or shredded paper in the first bin. If using manure that is mixed with bedding, it will have a good carbon-to-nitrogen ratio and you don't need to add anything else, Andrews said. Thick layers of one material might not decompose quickly if you don't have a balanced carbon-to-nitrogen ratio, he added.
It's important for the pile to have sufficient moisture, Andrews said. Wearing gloves, squeeze the organic matter firmly in your hand. You should be able to squeeze a few drops out of it. If you can't, add water to the pile. If you can easily squeeze out a stream of water, mix in some dry organic matter. Turn the pile in the first bin with a pitchfork a few times during the first month as it heats up. The pile should heat to 130-140 degrees. When conditions are ideal, compost can heat up within one day, Andrews said.
After the pile cools down to an ambient temperature, transfer it to the second bin. It usually takes another two to six months to decompose or cure. Horse manure may take longer to break down if combined with sawdust or straw bedding used in the animal's stall. Wear gloves when touching compost and wash your hands afterward.
Spread composted manure in your garden in small amounts, about one-fourth to one-half inches deep. Thicker applications up to 1 inch deep might be justified in poor soil with low organic matter. To prevent pollution, store compost away from water sources and cover the pile with plastic when you expect heavy rain. Don't keep applying excessive amounts of compost year after year, Fery said.
If you have composting questions, call the Master Gardener Plant Clinic at the Southern Oregon Research and Extension Center at 541-776-7371.