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Compost battle can be fought in trenches

| Friday, March 1, 2013, 8:35 p.m.
A traditional compost bin like this requires more 'management' than  trench composting.
Credit: Jessica Walliser
A traditional compost bin like this requires more 'management' than trench composting. Credit: Jessica Walliser

Few things are better for the garden than compost. Rich in organic matter, teaming with beneficial soil life, packed with nutrients and incredibly adept at breaking up our clay soils, compost is king of the garden.

Many gardeners work very hard to create their own compost. They layer nitrogen-rich grass clippings and carbon-rich leaves or straw. They toss in kitchen scraps and mix in a healthy dose of yard waste. Then they turn it (sometimes religiously), check its moisture content, monitor its temperature. Or, “less devoted” gardeners simply let the pile sit there and decompose in its own good time. Either way, what was once a living thing will eventually turn to compost.

But what to do if your municipality (or your spouse or neighbor) won't let you have a compost pile or even a neat-and-tidy compost bin? If that's the case at your house, let me introduce you to trench composting.

People have been trench composting for thousands of years. Folklore tells us that the Native Americans practiced it when they buried a fish beneath a mound of corn plants. Colonists did it when they buried their kitchen scraps beneath their gardens or in their fields. While I don't suggest burying fish (or any other kind of meat, for that matter) in your garden these days, you can get the same soil-building effects by burying plant wastes instead.

At its core, trench composting involves burying waste and waiting for it to decompose and add nutrients back to the soil. Trench composting is so much easier than building a compost pile. There is no need to turn it at the right time or spread it out when it's finished. You simply bury the waste, cover it and forget about it. The earthworms and microbes do all the work.

As with all things gardening, everyone has a favorite technique. Whether you do it in an individual hole, as the Native Americans did, or on a large scale, one rule remains the same: The composting ingredients should be buried 8 to 12 inches beneath the ground. This means that how deep and how wide you dig your trench depends on how much “waste” you have to compost.

Sometimes called hole-composting, small-scale trench composting involves digging an individual 12- to 18-inch-deep hole and tossing in a day's kitchen scraps. Fill the hole partway with scraps, then top it off with the backfill soil. Chopping up the scraps first results in faster decomposition but isn't necessary.

Larger-scale trench composting involves digging a long, deep trench and either tossing in the yard waste and covering it a little at a time (working from one end of the trench to the other as the season progresses), or digging a trench, filling and covering it all in the same afternoon.

In either case, if the pieces are small, it may only take a few weeks to fully break down. Larger pieces can take a few months. The rate of decomposition depends on your soil life, the soil temperature, and the amount of moisture present. Another benefit of trench composting: You can plant right over it without having to wait for it to decompose.

It's important to track the location of previous trenches and keep a rotation plan of sorts so you know which parts of the garden have been amended and which have not. With hole-composting, this is more challenging but perhaps not as critical.

If you rototill your garden, don't start any new trenches close to the time of tilling. You'll find that with regular trench composting, the need to till is eventually eliminated. Digging the trenches serves to loosen the soil and all the additional organic matter the compost provides creates a crumbly, friable soil without tillage. Not to mention how good all that soil life is at aerating and turning the soil.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio. She is the author of several gardening books, including “Grow Organic” and “Good Bug, Bad Bug.” Her website is

Send your gardening or landscaping questions to or The Good Earth, 503 Martindale St., 3rd Floor, D.L. Clark Building, Pittsburgh, PA 15212.

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