Trench composting is a method of cold composting where, as the name implies, one digs a pit or trench, fill it with organic materials and leave it for nature to do the rest.
The compost pit should be a foot deep and once you have about 4-inches of organic materials in it, you fill it with soil. It is a really simple way to deal with kitchen scraps – i.e. vegetable waste and fruit peelings – as it does not require turning and constant checking as with other methods of hot composting.
The length of time it will take for the compost to be ready depends on the materials you are composting as well as on the temperature. With pit composting, the compost is ready in as soon as a month or as long as a year.
Some seasoned gardeners who use trench composting dig their trench around trees’ drip lines. This is advantageous to the trees as their roots can readily access the nutrients from the composting material.
Finished compost from this method cannot be harvested, unlike with other methods of composting such as bin or heap composting. It can however be used to enrich an area you want to plant in so the trench or pit is best made near the planned planting area. Be prepared for some extra digging.
If you are composting high carbon-content materials which need a lot of nitrogen to decompose, this will result in the nitrogen for plants being depleted. This can be remedied by adding bone or blood meal to the material.
Or, you can just let your trench lie fallow for 1 year after filling it in. This ensures that the compost is complete and all nutrients will be available to your plants.
Trench Composting the English Way
There is a variation to pit composting called the English System.
If you have a larger area where you can set up your garden, you can try this method.
Prepare the area by dividing it into three rows. Each row should be about 1 foot wide and as long as you want.
These rows will be your (1) trench, (2) path and (3) planting area. The purpose of each row will be rotated every year. See the crude and unprofessionally made figure.
So in Year 1, you make the TRENCH and you either have PLANTS existing or none yet. Just be sure there is a PATH between the trench and the planting area.
On Year 2, the trench becomes the PATH to allow the nutrients to completely breakdown and be incorporated into the soil. The previous year’s path becomes the PLANT area and the former planting area is now the TRENCH for compost.
On year 3, the trench in Year 1 is the PLANT area – by now that area is rich in nutrients with very manageable, well-structured soil. The previous year’s planting area is now the TRENCH and the former trench the PATH.
As usual, the trench should be 1 foot deep and once there is 4-inches of organic material in there, fill it with soil. This will keep pests like rodents and even your own pets from getting to the compostable materials.
If you continue doing this cycle, in a few years’ time, you will have garden soil that is compost enhanced, healthy, well-structured, very good at retaining water and nutrients that crops will love and thrive in. By then, you could expand your garden and plant in the whole area.