Trench Composting: The Lazy Gardener’s Secret to Rich, Nutrient-Packed Soil!

If you’re looking for one of the simplest ways to compost, you’ve stumbled across the right method here!

Trench composting may involve a bit of digging, but it requires little thought about anything else. 

Like all composting, it’s a great way to improve soil structure and fertility, and I find it particularly useful when the conditions are not right for hot composting. 

In this post, you’ll find several different ways to trench compost, and we’ll explore the pros, cons and best times use this composting method.

What is trench composting?

Trench composting involves digging a trench or hole, dropping in organic matter and covering it up with soil. 

Most sources will tell you that it is an anaerobic (without air) composting method. 

The idea here is that because when air is cut off by the soil, anaerobic bacteria break it down. This is a slower process than aerobic composting. 

While it seems to make sense that without-air composting would take place, I can’t find a lot of evidence to support the theory. In fact, it’s possible that some oxygen is provided by the soil, and also that a lot of the breakdown is carried out by microorganisms and physical decomposers (such as worms) in the soil.

Six Trench Composting Methods

For such a simple method of composting, there are quite a few variations. Here’s six, with instructions on how to use each of them:

Simple trench composting

Best for: Beginners or small-scale composting.

What you need:

• Garden spade
• Organic material
• String (optional)

1. (Optional) Mark out where you want the trench to be with string.
2. Dig!

3. Place organic material into the trench. 

4. Cover with soil.

5. Mark where the trench is so you don’t forget!

Watch the short video below to see just how quick and easy this composting method is!

Deep trench composting

Best for: Larger quantities of waste, layered over time.

Deep trench composting does exactly what the name suggests. It’s a deeper trench, and usually involves layers being built up over several weeks.

Here’s how it works:

1. Dig a trench in your soil. Aim for at least 18 inches, and up to 24 inches. Do this in daylight hours, just in case your neighbors think you are burying a dead body 😉
2. Traditionally, you then add food scraps. However, as we’ll see you can add most organic materials. You can also balance this out with higher carbon materials such as leaves and shredded paper.
3. Add an inch of soil then put a barrier such as a pest-proof mesh on top to stop pests. 
4. Continue layering until you have nearly filled the trench. 
5. When there are just a few inches left, fill in the soil until the trench is full. The add some more soil on top to allow for settling. 

Why it works: This method creates deeper, nutrient-dense layers over weeks or months.

The English Method of Trench Composting

Best for: Vegetable gardens with plenty of space where you can rotate planting areas.

Also known as the rotating method of trench composting, the English method involves dividing your plot into three strips. One strip of soil is used for trench composting, one for paths and one for planting. The strips are then rotated each year.

Here’s how to do it:

1. Divide part of your vegetable garden into three strips. One will be your trench, one will be your path and one will be for growing in. 
2. In the first year, fill the trench with food scraps and other compostable materials as usual. Use one of the other strips for planting and one for a path. 
3. In the second year, convert the composting trench to a path, the planting strip to a composting trench and the path to planting. 
4. Repeat the process in the third year. 

Check out the infographic below to see an illustration of the method.

Pit Composting (Dig and Drop)

Best for: Small amounts of smelly waste.

Pit composting is simply the process of digging a hole in the ground, filling it with waste material and then covering it with soil again. 

Why I love it: It’s my go-to method for quick composting in winter when materials like cooked food scraps can’t go into a cold compost pile.

Worm trench composting

Worm trench composting involves digging a trench and adding food scraps and other organic material. You then add worms (or worm cocoons) to the trench.

The worms consume some of the organic material, helping to speed up the decomposition process. 

Tip: Even if you don’t add worms, some will be naturally attracted to your organic waste and play a part in decomposing it. Adding large quantities of worms or worm cocoons will increase the speed of the process and create more nutrient rich castings, but it is not essential for the every-day gardening.

See Red Worm Composting for a detailed description of worm trench composting.

Raised bed trench composting

Great for: Raised beds in polytunnels.

Most of my garden consists of regular veg beds, but in my polytunnels I have raised beds. While I usually mulch these beds, when I do use trench composting I use the following method: 

1. Cut down and put aside plants at the end of the growing side. 
2. Dig a trench across the whole length of the raised bed, putting the soil aside. 
3. Place cut-down plants in your trench. 
4. Add any other organic material you have to hand.
5. Replace the soil. 

Some raised bed gardeners take all the soil from the top of their beds and put it to one side. 

Some gardeners prefer to completely replace the compost from their polytunnel beds every few years. The photo below is from a friend’s polytunnel, when we took away the top level of the bed (which was all compost) and replaced it with manure in the autumn, before leaving it to rot down over the winter.

In theory, simply top mulching the bed should be the best option, as it avoids damaging the intricate network of funghi that provide nutrients to plants. That said, my friend’s tomatoes were really, really good the next year!

For a more in-depth guide see Farm Life’s guide to trench composting in raised beds or check out the video below.

What to put in your trench 

You can generally be pretty free and easy with what you add – after all, the whole point is for simplicity. 

That said, it’s a good idea to add both high nitrogen and high carbon materials if you can, and there are some organic materials which you should best avoid. 

High nitrogen materials (greens)	High carbon materials (browns)	Materials to avoid (or dig deep and/or cover with mesh)
Fresh grass Vegetable peelings Fruit scraps (e.g., banana peels) Coffee grounds Weeds (without seeds) Manure from herbivores (e.g. chicken, cow, horse) Plant trimmings Seaweed or kelp	Brown leaves Brassica stems Straw/dried grass Sawdust from untreated wood Dried grass Pine leaves Corn stalks or husks Pine cones	Meat Fish Weed seeds Diseased plants (these are better hot composted) Plastic or synthetic materials Most ‘compostable’ bags

You can find many examples of high carbon and high nitrogen materials in our Carbon : Nitrogen ratio tables. 

How good is the compost it makes?

Anaerobic composting can create compost that is lower quality than aerobic composting. 

However, as we’ve seen, it’s possible that aerobic composting does take place in trench composting, and I’ve had some great results when I’ve used it in my own garden. 

There’s little research to compare trench composting to other forms of composting, but one Indian study did report that trench composting produced compost with more nutrition than surface composting. 

I haven’t been able to see what type of surface composting the researchers used. However, Khalida et al also argue that more nitrogen is retained in trench composting than in surface composting. 

When to use trench composting

You could, of course, choose to use trench composting all the time, and if you’re looking for a simple, no-thought way to compost waste, it’s a perfectly good option. 

Even if you prefer regular composting, though, trench composting has its time and place. 

I personally find regular composting easiest to do from the spring through to the autumn. The volume of material I get from the garden, combined with warmer temperatures, makes it easier to generate the heat needed to rapidly break down materials. That’s especially important with more challenging materials like fish remains and cooked food scraps. 

In the winter my compost is likely to be cooler and wetter, and with a limited amount of material being generated it’s harder to get compost hot. 

That’s when I prefer to dig more challenging material into the garden, often with a simple hole rather than a complete trench. 

Tips and tricks

Heap the soil higher over the trench

Bear in mind the material in the trench will sink over time.

With that in mind, it’s a good idea to heap the soil a little higher over the trench than it is on each side.

Cover the trench with mulch

After the trench is full, cover it with mulch or a layer of leaves to help retain moisture and prevent weed growth. 

Cover pits with wire or a stone

Pits are easier to protect than trenches because of their smaller size. 

If you have buried any smelly materials, consider covering it with a barrier to stop pests.

Use a post-hole digger to create a line of pits

A post-hole digger can be an efficient way to create lines of pits in a vegetable patch or garden. 

This saves the work of having to dig a pit (and remember where they are!) each time you have material to compost. 

Shred materials before adding them to the trench

Materials break down faster when they are cut up or shredded. 

Sow a cover crop

While the normal advice is to wait a year before sowing, some trench composters do sow a cover crop such as lettuce or radishes.  

This has the advantage of reducing weeds and helping to reduce water loss. It can also help the beneficial fungi in the ground. 

Depending on what you plant, you might also get some food out of it!

Five advantages of trench composting

Viable in more places

In some places traditional composting is prohibited. In these places, trench or pit composting is ideal, as it keeps organic waste out of sight (and mind) and runs little risk of odors. 

Little equipment needed

Other than a spade or fork (which you probably have already) you need very little equipment to dig a trench! You certainly don’t need to invest in compost bins. 

Simple

Traditional composting is not difficult, but you do need to include a roughly even mixture of high carbon and high nitrogen materials, ensure the bin or pile is aerated, and keep an eye on moisture levels. 

It’s still a good idea to include both carbon and nitrogen-rich materials in a trench if you can, but other than that, the process requires little thought and zero maintenance. 

Reduced water usage

Hot, dry climates can be challenging for composters, as the compost can dry out. However, when the material is covered with soil, water loss is minimized, and you do not need to add water to the compost. 

Odour control

Traditional composting can cause bad odors if it is not managed correctly, or if an anaerobic composting process is used. By covering material with soil you usually eliminate all unpleasant odors from the composting process. 

Six Disadvantages of trench composting

Impact on the soil

Much of the benefits of compost do not come from directly feeding the plants. 

Instead, the compost improves soil structure and feeds a network of fungi. These fungi extract nutrients from the soil and channel them to the plant in exchange for…

However, you disturb the microorganisms in the soil when you dig, which is why no-dig and no-till methods have become so popular in recent years.

May produce methane

Compared to aerobic composting, anaerobic composting releases huge amounts of methane. In fact, methane is a big part of the reason we are encouraged to compost for environmental reasons.

Aerobic composting does release some gases – that’s unavoidable – but it releases far less methane.   Still, as discussed earlier, not every source agrees that anaerobic composting takes place in trenches.

Time and space required

While you are trench composting, you can’t really use the space you are composting in. 

Anaerobic compost takes longer to decompose, and fresh compost can be high in phytotoxins, which can damage plants. 

What’s more, when it’s full, the ground tends to sink as the material decomposes. (You can partly compensate for this by adding more material.)

The general advice is also to leave the space for 6 months to one year while the material decomposes.

I’ve never done this, as I’m too impatient and space is too valuable, and I’m prepared to sacrifice some crop quality in order to fully use the space I have available!

Still, in contrast, aerobic composting takes place outside the vegetable patch. 

If you are using a bin, it’s a very efficient use of space and allows you to ensure that your veg bed is being fully used at all times. 

So if maximizing the amount of space available to you is more important than the ease of composting, I’d suggest using a compost bin instead. 

Pest control (depending on materials used)

Covering smelly materials with soil usually deters larger pests. However, I’ve had a couple of failures where an animal — probably a fox — managed to sniff out the waste and dig it up.

In hindsight, I was being a bit too lazy and didn’t dig the hole deep enough. If you’re adding smelly materials like meat or fish, dig deeper and consider using a barrier, such as wire mesh or stones, to keep pests at bay.

Weed seeds

Hot composting processes – and some anaerobic composting processes – kill weed seeds. 

However, when you dig weeds into the ground, any seeds attached to them could re-sprout in the future. 

Wrapping up…

If you really don’t want to think that hard about composting, trench composting might be the option for you!

Limited research – but lots of experience – suggests that it’s an excellent way to improve your soil, and may be more effective at retaining some nutrients such as nitrogen. 

On the other hand, if you want to maximize the use of space in your garden, you may be better off with a compost bin.

Of course, there’s no need to limit yourself to just one type of composting!

You might also find it worthwhile to experiment with different types of composting, finding out which ones suits you and your soil!

FAQs

How long does trench composting take?

That’s always a matter of debate – although typically composters will tell you six to twelve months. The truth is it depends on a number of factors. These include:

The material you use: Woody materials take longer to decompose because of their high lignin content.
The size of the material: Large pieces of material take longer than smaller pieces of material.
What you are growing above the trench: Some plants are more tolerant of decomposing material than others (think of the plants you see growing in your compost pile!)

Can you compost pet waste in a trench or pit?

Yes, you can. However, the Compost Education Centre advises not doing so in vegetable patches, and limiting trenches and pits for pet waste to ornamental beds. This is to avoid pathogens infecting your vegetables.

Can I trench compost in the winter?

You can usually trench compost in the winter if the ground is not frozen. When it freezes, the ground is usually too hard to dig. 

It may also take longer for the organic material to decompose due to the colder temperatures. However, some composting does still happen in winter, and the layers of soil could help protect the organic material from the extremes of cold above the soil.

You can speed up the process by insulating the trench with straw or other organic material.

Can I trench compost in a container?

Yes, you can trench compost in a container, such as a large pot or bucket. Simply fill the container with organic material and soil, and then cover it with a lid or mesh to prevent pests from getting in. 

Can I put plants in a container when I am trench composting with it?

I’ve tried this myself. It’s not ideal, as the soil or compost sinks down as the material decomposes. However, it is possible. 

Can I use trench composting to compost large branches or tree trunks?

My own experiments with branches have shown very poor results. That’s probably because branches take a long time to rot down, and a large amount of wood can rob the soil of nitrogen. 

However, there is a rather more specialized form of composting, known as Hugelkultur. This usually involves building a large bank with wood/logs e.t.c. and covering it with organic material and then soil. 

While a bit more complicated than simply digging a trench, it can have good results in the long term. 

Read next

Looking for the laziest ways to compost? Here’s 7…
13 Composting Methods – Plus How to Choose The Best One

External resources

Compost Education Center Trench Composting