Trench composting is a method of making compost that is just as simple as you might imagine.
All you do is dig a hole and bury your compost materials anywhere in the yard or garden where you’re not currently growing something.
Then you forget all about it while the organic materials gradually decompose over a period of 6 months to a year.
This method works particularly well for people who want their organic matter out of sight while it is decomposing. A trench is also a good place to get rid of those weeds you have pulled up. If buried deep enough, the weed seeds won’t be exposed to sunlight, and won’t re-grow.
Why is compost important for the soil?
It is not only important, but it is essential, because: 1. It contains the key plant nutrients – nitrogen (N), phosphorus (P) and potassium (K), often written as NPK.
2. It improves the organic matter in the soil as the materials break down into the earth.
3. It helps the soil hold both water and prevents compacted soil;
4. It makes trace elements, also known as micronutrients, readily available to new plants after the compost breaks down.
What material is needed to make organic compost?
1.Weeds, grasses (both green and dried out will work) and any other plant materials cut from fields, or when clearing paths from weeding.
2. Wastes from cleaning grain, cooking, making food and different drinks, particularly coffee, tea, home-made beer, etc.
3. Crop residues: stems, leaves, vegetable scraps, cereals, herbs.
4. Garden wastes: old leaves, dead flowers, hedge trimmings, grass cuttings, etc.
5. Dry grass, hay and straw left over from feeding and bedding animals (animal bedding is useful because it has been mixed with the urine and droppings of the animals), or the remains from rabbit, hamster or bird cages.
6. You can even bury meat or dairy waste in small amounts, unlike with traditional composting.
Good places for your trench compost include areas where you want to set up a future garden bed or between rows of existing garden beds. You must avoid muddy areas or low spots with wet soil and poor drainage. It is important to stay away from existing root systems when digging composting holes.
Tree and shrub roots can expand up to twice the diameter of their above ground canopy. Chopping their roots with a shovel creates areas for pests and diseases to enter, ultimately weakening and possibly injuring or killing your plant. If you’re unsure how far roots may have spread, resort to digging compost trenches in garden beds.
3 different methods of trench composting
1 Dig random holes, 2. Fill trench rows in garden beds 3. Rotate trenches over a 3-year period to improve an expanded planting area. We recommend that you use the basic anaerobic trench compost recipe that follows for whichever method you choose. How deep and wide your digging is 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.
After choosing your favorite type of trench composting:
1. Dig the trench, keeping the soil that you remove.
2. Start with browns on the bottom, alternate layers of brown and green materials, moistening as you build.
3. Spread a 1-inch layer of your reserved soil between layers of browns and greens.
4. Cover with 4 to 8 inches of soil. If you plan to retrieve the compost later, mark the area so you can find it.
Usually, your compost trench should be around one foot deep. The area of the trench hole is determined by the amount of organic matter you want to drop. Keep in mind that the compost will be finely chopped and piled to a height of 4 inches in the bottom of the hole when estimating the hole’s size. Chop your composting materials finely so they will break down faster, or expect for the composting to take a lot longer.
The underground composting proceeds more slowly than the above-ground one, so maximizing the surface area of your scraps is vital for speeding up the process. Kitchen scraps can be ripped apart by hand, chopped with a knife, or even pulverized in a food processor. Yard scraps can be broken down using a lawn mower. Pieces should be no bigger than 2 or 3 inches in any dimension.
Add all of the organic materials to the compost hole. Pile your food scraps and garden waste into the hole to a depth of about 4 inches. Make sure your carbon-rich materials (such as paper and dried leaves) are mixed thoroughly with your nitrogen-rich materials (like vegetable scraps and fresh grass clippings), as you will not be turning the underground pile.
Place a temporary cover-board over the hole if you plan to add more scraps over time. However, if you want to be able to continually add scraps to the compost pit, cover the compost with a thin layer of soil or carbon-rich material. Then place a wooden board over the hole to prevent anyone from tripping into it. Be careful not to add materials to a depth of more than 4 inches, as this will make it difficult to adequately cover the compost with soil later on.
Finally, cover your compost trench with soil. Once you have finished adding your organic scraps to the compost pit, you can backfill it with the soil you removed. Add the soil on top of the compost, filling the pit until it is again leveled with the surrounding soil. You can recover it with sod or seed with grass. Remember to keep the compost trench wet while it is decomposing.
Underground compost decomposes slower, because it doesn’t have access to as much fresh oxygen as above ground piles. To speed up the process, make the area gets watered sometimes. Soak the ground above the compost with a garden hose water during dry weather. If the hole is too dry, it will prevent microbes from breaking down compost scraps and it just becomes a tomb. But if the area is kept fairly moist, underground compost should be fully decomposed in about 12 months, and sometimes sooner.
You can seed plants above the compost after it has decomposed. A major asset of underground composting is that you don’t have to perform any extra steps to harvest the compost or amend the soil. The best way to take advantage of this is to plant your plants directly over the area where you composted your scraps. In fact, each season you can cycle the locations where you grow plants and compost. This makes your planting soil always freshly amended with organic matter!
If space allows, you may dig the trench in advance, in form of a straight row or as a “block” section of a bed. That makes it very convenient for stage-filling, by pouring in compostables whenever you can, thus gradually filling the trench.
But, if space is limited, or if you don’t produce a lot of material to compost, you might find it more convenient to just bury small batches when you have enough organics to make it worthwhile to dig a small hole.
Selecting a good trench composting site
1. It should be in an accessible place where it’s easy to take the materials, including water and urine, as well as for monitoring it.
2. The site should be protected from strong sunlight and wind. For instance, it can be in the shade of a tree, or on the west or north side of a building or wall.
3. The trench should be always marked with a ring of stones or a fence of branches so that people and animals do not fall into it.
4. The site should be protected and away from where floods can come.
If you have a garden, no matter its size, you can use it to recycle both the vegetation of the season passing by and the left-over peelings from your kitchen in a simple trench. The best news about it is that there’s no need whatsoever for maintenance (such as watering or aeration), which is usually needed with regular composting. Once you make your trench, it’s just a matter of waiting and you’re done.