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It’s All in the Compost
By Kimberly Gomes

Excerpt from "3 Way to Improve Soil for Spring" SFGate, Feb 15, 2013

Compost Workshop in Kenya

Photo by Boaz Oduor
Compost workshop in Kenya

Compost fosters healthy plants and returns organic matter to the soil. SFGate asked John Jeavons, compost connoisseur, to share his favorite technique for feeding soil. If you choose this method, your garden will thank you.

Compost is organic matter that decomposes into nutrient-absorbent humus. Greens—the common name for wet, high-nitrogen materials—include kitchen scraps, grass clippings, green leaves, and compost crops. The counterpart—known as browns—consists of dried materials such as carbon-rich leaves and small amounts of straw.

Finding the right balance of (immature crop) greens and (mature crop) browns takes practice, but ultimately your pile should have a carbon-to-nitrogen ratio of 30:1, consisting of 45 percent greens, including kitchen waste, 45 percent browns and 10 percent soil, according to expert composter John Jeavons, director of the GROW BIOINTENSIVE program, a high-yield gardening method for plots 3 square feet and up, in Willits, CA.

Jeavons builds his pile on a new raised bed each year, so compost juices rotate throughout the garden. Besides adding microbes and nutrients, the right amount of compost can boost soil's ability to retain water. He says compost "is an amazing thing. It smells like fresh spring once it's fully composted."

The method
Compost piles need to be a minimum of a cubic yard to generate enough heat to decompose materials into humus.

Loosen the area 12 inches deep and cover with 2 to 4 inches of roughage such as twigs and small branches. Layer two 5-gallon buckets of mature, dry matter, such as straw or dried leaves. Thoroughly water the pile.

Top with two 5-gallon buckets of green material like grass clippings, kitchen waste and green leaves. Water the greens so they don't dry out.

Add 2 1/2 gallons of soil to hold in moisture and hasten decomposition. Water the pile and repeat the steps above until your pile reaches a height of 3 feet and cap it with one 5-gallon bucket of soil.

Continue to water the pile daily while it heats up. After about three to four weeks put a metal tomato stake down the middle. Let it sit for a few minutes before removing the stake to gauge the temperature. It should be hot to the touch. If using a compost thermometer, the pile should be around 129 to 139 degrees.

Return the stake to the pile and repeat daily for two weeks until the temperature drops from hot to the touch to significantly warm or 111 to 119 degrees Fahrenheit.

Turn the pile, moving the less-decomposed material to the middle; water daily. The pile will heat up again to about 119 to 129 degrees for 10 to 14 days before the temperature drops once more. After three to four weeks, review the material. Once the compost is dark brown and fully decomposed, apply to the garden by broadcasting it onto previously loosened soil. Using the spading fork, sift the compost into the top 2 to 4 inches of soil. Use no more than six 5-gallon buckets over 100 square feet.


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