How to Trench Compost [2020]

How to Trench Compost

Trench composting is a quick method of adding organic material to the soil that will decompose and fertilize the soil, retain moisture, prevent soil compaction and attract beneficial insects and organisms.

Why I Like Trench Composting?

Trench composting is simple and a quicker method than regular composting. Normally you would create a pile of organic material either in a backyard corner or in a compost bin. You have to mix green and brown materials together in a specific ratio, water and turn over several weeks for the material to decompose before using it as fertilizer. It takes a while and requires regular maintenance. This may not be a bad thing though? It’s exercise right?

Traditional composting takes more time and has extra steps in it. I like the directness of trench composting. You bury the plant material (future compost) directly under the soil you’re going to plant vegetables in. It’s straight forward with the same results.

Another benefit of trench composting vs regular composting is you don’t attract insects that are undesirable like ants, flies, cockroaches, earwigs, etc. Composting on top of the soil or in a bin attracts lots of bugs like flies, ants and cockroaches. I prefer not to have more of these in my yard. Trench composting hides the organic waste below the ground where it is out of sight and does not produce an odor that insects find attractive.

Trench Composting

Here’s one of my trench composting sites in my backyard next to one of my vegetable gardens. I threw some pieces of carrots in this trench. I’ll mix it with more plant material before covering it up.

Trench Composting close up

Trench Composting Details

The depth of the trench doesn’t matter too much but it should be at least 8 – 12 inches deep and 15-20 inches is even better. The trench needs to be deep enough to prevent it from drying out. You want it to be moist so that bacteria, microbes and worms will be attracted to it. Bacteria, microbes and insects help decompose plant matter. I water my trench composts daily. In about 3 months they will be totally decomposed. This makes fantastic fertilizer for plants. It’s kind of fun too.

Spot Trenching Method

Another version of trench composting is called Spot Composting. The difference is the shape of the excavation or hole. Spot Composting is done with a round hole in the ground instead of a long, narrow trench. You can use a shovel and dig a hole or a fence post hole digger. It works the same way but may be more appropriate in certain locations where a trench isn’t practical.

Spot composting is ideal when you have a small amount of organic waste and want to put it to use immediately. A trench requires more organic waste than spot composting. You can also spot compost alongside vegetable plants like tomato plants that require large amount of Nitrogen. You can select where you want to add organic compost in an established garden easier with spot composting.

What to Use in a Trench Compost.

You can use kitchen scraps for the trench compost. The smaller the pieces the faster they will decompose and then fertilize. Ideal materials are greens like lettuce, spinach, carrot tops and bottoms, cabbage, green beans, cucumber slices or pieces, celery, etc. If you want it to decompose faster then throw the scraps in a blender with some water and blend well. Now you can pour the mixture in the trench and cover with soil.

If you have weeds, you can safely compost them in trenches or spots. Normally you would not want to throw weeds in your compost pile because the seeds will remain and most likely grow once you spread the compost in your garden or yard. That’s not a good scenario. The better way to compost weeds is to bury them. They will not grow when buried 12 inches deep. I always spot compost weeds.

What NOT to Use in Trench Composting

I recommend not using any animal products like meat, blood, dairy products or animal feces from dogs or cats. I only like using PLANT waste when composting.

When to Start a Trench Compost

I usually start a trench compost site 2 months before I plan on planting seeds. This gives the material time to decompose and start fertilizing the soil. It’s a good idea to cover the trench soil with some mulch to assist with water retention. This speeds up the decomposition process.

It’s good habit to start trench composting in the fall or as soon as your garden is done producing. Decomposition in the cooler temperatures of fall will be a little slower but will still complete. Then in the Spring, the soil will be primed for planting.

You can start planting on top of a trench compost anytime but I usually wait about 30 – 60 days after burying the compost material. I then cover the top with 2-3 inches of mulch and plant the seeds. The mulch keeps the soil moist and cooler. Seeds will germinate in 7-10 days every time.

Benefits of Trench Composting

Trench composting not only enriches the soil but also keeps the soil from getting hard and rock-like. It allows water and air to penetrate the soil.

Trench composting also attracts beneficial insects/organisms like earth worms, ladybugs, nematodes, beneficial bacteria and microbes.

Earth worms are great. They aerate the soil when the borrow. This allows water and air to penetrate the soil. Plants need air and water to get to the roots in order to grow. Worms also produce castings [worm poop] that is an excellent organic fertilizer. One of the best known to man. Your plants will love it.

**** Remember to mark your trench and spot composting areas so you don’t accidentally dig them up.

Disadvantages of Trench Composting

  • Have to dig trenches or holes
  • May run out of places to dig holes or trenches
  • Can’t dig in areas where you have compost buried.
  • Organic scraps will decompose more slowly than above ground compost pile or bin.
  • Have to mark areas where you have trench or spot composts
  • Have to bury the organic scraps at a certain depth [12 inches]
  • Could attract pests
  • Can release methane gas as a byproduct of decomposition