When Should I Spread Out My Composted Soil?

Adding fresh waste lengthens the time until the compost is ready.
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After establishing your compost heap, knowing when to spread that compost on your garden can be challenging. Large pieces of organic material that haven’t composted completely continue to decompose in the garden, temporarily robbing plants of nutrients. If compost hasn’t “cooked” long enough, plant diseases and pathogens may still be active and attack healthy plants or spread to vegetables you want to harvest. Inspect your pile regularly, and watch the calendar to determine when to use your compost.

Compost Pile

Your compost pile began as a mixture of nitrogen-heavy waste, such as grass clippings, coffee grounds and fruit and vegetable peels, and carbon-heavy waste, such as dried leaves and paper. Microorganisms, worms and a variety of insects moved in and, with the aid of water, oxygen and time, turned that waste into a nutrient-rich natural fertilizer. According to the U.S. Environmental Protection Agency, a backyard compost pile can take up to two years to be ready for spreading. How carefully you monitored this pile directly affects how quickly the compost matures. (See References 1 and 3.)

Speeding Up the Process

Moisture content and oxygen flow play important roles in composting. The organisms responsible for decomposition need adequate water to survive and to transport substances necessary for decomposition. Keeping the pile moist ensures that decomposition continues. Also, decomposition is an aerobic reaction that requires plenty of oxygen. Turning the compost every week with a pitchfork or hay fork not only aerates the pile, supplying oxygen, but also distributes moisture evenly through the pile. If you maintain proper moisture and oxygen levels, your compost could be ready in one to four months. (See Reference 2.)

Slowing Things Down

Several factors may cause your compost to slow decomposition. Overaerating, or turning the pile too often, without keeping an eye on the moisture content dries out the pile, stopping decomposition. Not aerating the pile allows it to compress, eliminating all air flow and aerobic activity and again halting decomposition. Also, continuously adding waste begins the decomposition process again, lengthening the time for even a well-maintained pile to be ready. Set up at least two compost piles, leaving one pile to “cook” or decompose while adding fresh waste to the second pile.

Is It Ready?

Finished compost will be dark and rich in color, crumbly in texture and earthy smelling. It might have small bits of uncomposted material, but you should not see large pieces of yard or kitchen waste that haven’t decomposed. Once your compost pile has reached this consistency, the EPA recommends letting it sit an additional two weeks before spreading it (see Reference 2). The New York City Department of Sanitation’s Bureau of Waste Prevention, Reuse & Recycling recommends using the "bag test" to check whether your compost is ready for use: Put a small amount of compost in a zip-close bag for three days, and then check it for unpleasant odors. If the compost smells sour or sharp, then the decomposition process is still under way; if it retains its earthy, soil-like smell, it's ready for use. (See Reference 4.)

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