How to Kill Seeds From Cow Manure

Remove a section of turf where you will add the manure compost pile, using a spade to cut through the turf layer, and scrape up the turf in strips. The size for the compost pile depends on the amount of manure you wish to process, but larger piles generate more heat. For best heat generation, the pile should measure about 5 to 7 feet wide at its base and 3 to 4 feet tall. Do not make the compost pile in a low-lying area of your yard where water can pool up in the pile. At the same time, a shaded area is best for compost because it keeps the pile from drying out too quickly.

Spread the cow manure across the bare soil. If you have plain manure, mix the manure with 30 to 50 percent straw, dried leaves, or other carbon-rich, organic material. Cow manure gathered from a barn stall likely has a good amount of straw or hay mixed with it, so you don't need to add as much, if any, straw to the manure.

Spray the manure and straw with a garden hose just until damp. Turn the pile using a pitchfork or shovel to ensure even moisture throughout the pile.

Work the manure and straw mixture into a large pile measuring about 5 to 7 feet wide and 3 to 4 feet tall. Pack the pile tightly, using a hand tamper or the back of a shovel. Dense nitrogen and carbon materials heat up faster and at higher temperatures than loose compost.

Cut two pieces of 2-inch diameter PVC pipe about 1 foot longer than the compost pile height. Drill 1/2-inch diameter holes through the pipe, spaced about 6 inches apart along the length. Push these two pipes down into the center of the pile where they act like chimneys to allow oxygen flow to the center of the pile. Frequent turning of a compost pile allows oxygen ventilation, but the pipes provide additional ventilation, so you can allow the pile to generate enough heat to kill the seeds.

Monitor the temperature at the center of the compost pile daily, using a compost thermometer with a long stem that can probe the pile. To kill seeds, the compost pile should reach an internal temperature of at least 135 degrees Fahrenheit, but not over 160 degrees. Spray the pile as needed to maintain slightly damp moisture; you should not be able to squeeze water from the compost when you squeeze a clump in your hand.

Turn the manure compost pile a few days after the inside temperature reaches 135 to 150 degrees, which is hot enough to kill harmful pathogens and seeds. The manure and straw on the outside of the pile should be turned into the center of the pile; the compost at the center should be moved to the outside of the pile. Create a second pile if the temperatures frequently hit above 160 degrees because this temperature can kill the beneficial fungi and bacteria -- these are essential microorganisms for heating the compost and decomposing the organic materials.

Turn the pile frequently to ensure all the manure and carbon materials compost evenly. Allow the internal temperature to rest at 135 to 150 degrees for about four to six days before turning the pile each time. Remove and replace the PVC pipe vents each time you turn the pile.

Stop turning the pile and put the manure to use in your garden when the pile no longer maintains hot temperatures above 110 degrees and the materials have broken down into smooth, finished compost.