Composting is typically done in a barrel or bin. The containers tend to be bulky, unsightly, and require periodic turning. Trench composting is a great alternative to bins and barrels. Trench composting is simple. Just dig a trench or any shape hole approximately 12 inches deep, add roughly four to six inches of compostable materials, such as kitchen scraps, and fill hole with the dug-up soil. That is all there is, no watering or turning the pile.
Putting the trench adjacent to the plants gives them nutrition right near the roots. This helps to develop strong roots which will help the plant cope during times of dry conditions. The only downside to trench composting is you may forget where the hole is. That is not a problem. Compost material breaks down in a few weeks. Since there is a small amount decomposing, you can plant right over it.
Compost bins can give off an odor. With trench composting nothing is visible and there is no odor.
I use this method in my vegetable garden. Along with rotating crops in the garden, I try to rotate the location of the trenches to amend the soil in the entire garden. If you rototill your garden, don’t start any new trench close to the time of tilling. Over time regular trench composting will eliminate the need to till. Digging the trenches loosens the soil, and the compost matter creates a crumbly soil without tillage. Not to mention the job that the worms are doing aerating and turning the soil.
What goes into a trench for composting? The short answer is what not to put in. Don’t trench weeds. Perennial weeds can regrow from sections of their roots. Annual weeds may have seeds that will grow when the seeds come to the surface from tilling. Avoid adding meat and dairy scraps. Pet wastes should not be added. Farm animal manures, like those from cows, horses, and chickens, can be trench composted, but don’t plant there for four or more months to avoid any potential pathogen exposure. Coffee filters, nonbleached paper towels and napkins, can be added as trench fillers. Grass clippings can be added but too many can generate a lot of heat. It is best to mix grass clippings with leaves first or layer them in with other ingredients. You don’t want too much of one thing. A variety of material will speed up decomposition.
More information on composting can be found in the NC State Extension publication Backyard Composting of Yard, Garden, and Food Discards.