Trench composting is one of the simplest composting systems used by gardeners. All you do is dig a trench, fill it with garden, kitchen, or yard waste, and then cover the filled pit with soil. No stinky, unsightly compost piles sitting around attracting bugs, neighborhood dogs, or rodents. The debris breaks down with the help of soil bacteria, fungi, and earthworms. The resulting organic mix provides fertilizer in the root zone of the plants growing in the bed. This composting system simulates an old soil-building technique called double digging. It works great with a raised bed garden.
Advantages of the Pit Composting Method
- It puts the compost in the root zone of the plants.
- The loosened soil provides an ideal medium for plant roots to grow.
- Added organic material improves the moisture-retaining ability of the soil.
- This composting method is useful for residents of communities that disallow compost piles.
Some Disadvantages of Direct Composting
- Digging the trenches is labor-intensive.
- Areas of the garden may be out of production.
How to Compost Directly in the Garden
If you grow your vegetables in raised beds this system is easy to incorporate into the garden. It is best to begin the system in late summer or fall, but early spring will also do. Dig a trench across one of the beds about 8 inches to 1 foot deep and any width that is convenient. Save this soil in a bucket or wheelbarrow. Incorporate a slow-release organic fertilizer into the bottom of the pit, if desired. Using the shovel, break up the soil at the bottom of the pit, working the fertilizer into the soil. This not only puts fertilizer deep into the soil, it also loosens the subsoil. Doing this gives plant roots an easy-to-penetrate zone to grow. Add the plant or kitchen debris. The material can include leaves, grass clippings, and any kitchen scraps that do not include meat, bones, or fat. You can also add garden debris like corn stalks, spent tomato plants, or other plant material. After filling the trench level with debris, cover it with dirt from a trench dug next to the filled one. If composting in the fall or early spring before planting the garden, continue the digging until you finish the entire bed. Fill the last trench with the saved soil from the first trench that you dug.
Rotation in the Garden
During the growing season, you can trench compost in spots between crops or in areas that become empty due to crop harvesting. Just dig a small hole, being careful not to disturb root systems of nearby crops, bury the kitchen scraps, and cover with soil. As crop plants in the beds mature in a bed, harvest the crops; remove the plants and trench compost the bed. Wait a couple of weeks to replant after covering the trenches with soil. In this way, you will double dig/trench compost all the beds during a growing season or two.
For a description of how to use this system in the garden, visit the author’s website, Abe’s Beer Garden.
Other Sources of Pit Composting Information:
Why You Should Compost in Trenches About.com
Composting Methods – University of Illinois
Trench Composting – Home Guides