The Basics of Pit (or Trench) Composting
If you live in a place where digging holes in the ground is no big deal, you can make a pit compost. The following info helps you add anaerobic composting to your repertoire. Good choices for your pit compost include areas where you want to add a future garden bed or between rows of existing garden beds. Avoid marshy areas or low spots with wet soil or poor drainage.
Stay away from existing root systems when digging composting holes. Tree and shrub roots easily expand to twice the diameter of their aboveground canopy! Slicing through roots with a shovel creates easy wounds for pests and diseases to enter, ultimately weakening and possibly killing your plant. If you're unsure how far roots may have spread, stick to digging compost trenches in garden beds.
Depending upon what you want to achieve, you can employ several different methods of pit or trench composting, such as digging random holes, filling trench rows in garden beds, or rotating trenches over a three-year period to improve an expanded planting area. Use the basic anaerobic trench compost recipe that follows for whichever method you choose.
How deep and wide to dig depends on how much organic matter you have to compost, what kind of material it is (landscape waste versus kitchen waste), how easy it is to dig, and whether digging pests might be an issue.
Follow these steps to create a pit compost.
Dig the hole or trench, reserving the soil that you remove.
Start with browns on the bottom, alternate layers of brown and green materials, moistening as you build.
Spread a 1-inch (2.5-centimeter) layer of your reserved soil between layers of browns and greens.
Cover with 4 to 8 inches (10 to 20 centimeters) of soil. If you plan to retrieve the compost later, mark the area with a stone or other reminder.
If you grow flowers, herbs, or vegetables in straight rows with plenty of space between them, dig and fill composting trenches between the rows. As the organic matter in the trenches decomposes, nutrients become available for nearby plants. Dig trenches early in the planting season before vigorous roots expand into the area. Alternatively, dig trenches at the end of your growing season, so material is decomposed by the next planting season.
Certain plants really thrive on soil that's rich in organic matter and water-holding material, particularly sweet peas, runner beans, zucchini, pumpkins, and squash.
Six to eight months before planting, dig a trench or pit where you plan to grow these crops, 18 inches (45 centimeters) deep. Fill with kitchen waste, newspaper, manure, and other retentive materials, then top with a 6-inch (15-centimeter) layer of soil, heaping it up to form a mound. By the time your planting season rolls around, the site will have settled and will be ready for seeds or transplants.