What You Should Not Use
Do not bury meat, fish, bones, dairy products, oils, greasy foods, or cooked leftovers with sauce or fat. These are the materials most likely to attract rats, raccoons, dogs, cats, and other scavenging animals. They also create stronger odors and break down poorly underground.
You should also avoid pet waste, diseased plant material, invasive weeds, and weeds full of seeds. Thick woody stems and large branches are usually too slow to be useful unless broken down very finely.
How to Make a Trench
A basic trench should be about 8 to 12 inches deep. That depth is enough to hide the material well, limit smell, and keep most animals from noticing it. The trench can be a straight row, a circle, or a small pit, depending on your garden layout.
Place the scraps in the bottom of the trench and spread them in a loose layer. Do not pack them tightly. A layer that is too dense can decompose slowly and create soggy pockets. After adding the material, cover it with at least 6 to 8 inches of soil. Firm the soil gently and water lightly if the ground is very dry.
That is all. Once buried, the soil life takes over.
How to Avoid Rats and Other Animals
This is one of the most important parts of trench composting, and it depends mostly on what you bury and how well you bury it.
First, never add meat, dairy, grease, or oily food. These are the biggest pest attractors. Stick to fruit, vegetable, and plant-based scraps.
Second, dig deep enough. Shallow trenches are one of the main reasons animals find buried waste. A trench that is at least 8 to 12 inches deep is much safer than a shallow one.
Third, cover the scraps completely with soil. Do not leave any food exposed near the surface. Even a little exposed material can attract attention.
Fourth, avoid burying very large amounts in one small spot. A huge concentration of fresh scraps can create stronger odors. It is better to spread material out or use several trenches over time.
Fifth, chop scraps before burying them. Smaller pieces break down faster and are less likely to sit underground long enough to attract pests.
If animals are a serious problem in your area, you can also place a layer of plain soil, then a few dry leaves, then more soil over the trench for extra cover. Keeping the area mulched can also help hide any scent.
When to Use It
Trench composting works whenever the soil can be dug. Many gardeners do it in fall to prepare beds for spring planting, but it can also be done during the growing season in empty spaces, between rows, or in future planting areas.
It is especially useful before growing heavy-feeding crops such as squash, pumpkins, cucumbers, tomatoes, corn, and melons.
When and How to Plant Afterward
Do not plant directly into fresh buried scraps right away. During early decomposition, soil microbes use nitrogen, and this can temporarily reduce what young plants can access. Fresh scraps can also generate heat and uneven settling.
A safe guideline is to wait at least 2 to 6 weeks before planting near or above a trench. In cool weather, or when the scraps are coarse and plentiful, wait longer.
For immediate planting, keep seeds and seedlings about 6 to 12 inches away from a fresh trench. After a few weeks, once decomposition has started, you can plant more closely. If the trench was prepared well in advance, the area above it can become an excellent planting zone.
When planting, make sure the topsoil is stable and crumbly. If the ground has sunk, level it first. Then plant as usual and add mulch to help keep moisture even.
