Be sure to check out Part I in this series: Vermicomposting Trenches: An Effective (and Protective) Outdoor, In-Ground Vermicomposting Method
Back in June we published an overview of vermicomposting trenches, including the set-up process for one of the two demonstration trenches we installed in late May. In this follow-up, we’ll:
- look at how the second trench was set up,
- cover the topic of ongoing trench maintenance
- explore common questions relating to vermi-trenches, and
- briefly look at “above-ground” trenches and other hybrid approaches.
Let’s dig in!
With trench #1, we wanted to showcase a deeper trench (likely close to 3 ft deep) with a thicker false bottom, containing a lot of woody debris. This is a great option for anyone that has a lot of yard waste, and has relatively easy digging and/or some machinery to help with the job.
We realize this won’t be the case for a lot of people - and that’s totally OK. Do the best you can with the soil conditions and resources you have available! Some form of trench is always going to offer more protection than no trench - so don’t obsess about it needing to be perfect (or exactly like ours etc).
Our “Trench #2” could be considered closer to a “typical”, home-scale vermi-trench. As was the case with trench #1, it was positioned in the middle of a narrow raised bed, and started in much the same way.
Remember, it’s always much better to start really narrow (especially close to the surface), since it’s easy enough to expand - but you can’t put soil back in place!
Even though this was more of a low-key / typical homeowner grade trench, we did want to test out the use of a small backhoe to see how much it might help with the digging. Ironically enough, we realized pretty quickly that this was overkill for a trench this size, especially one running through the middle of a small raised bed!
We also learned that if you are going to use machinery, it’s best to start the trench with it rather than using it to expand a trench you’ve started by hand. Almost right away, we ended up with a partial cave-in on one side, so we quickly discontinued using the mini backhoe, and simply finished digging manually.
We lucked out in terms of site selection for our deeper and shallower trenches. While there were certainly rocks removed while digging trench #1 (deeper one), far more were encountered in the second raised bed, which would have made the digging process a lot less enjoyable to say the least!
With less depth, we opted for a somewhat more basic false bottom in this trench - starting off with a basic layer of wood chips.
Over top of this, we added a lot of bulky, brown cardboard (a material most people have good access to) along with a smaller amount of egg carton cardboard.
The woody materials in the very bottom are a great way to provide some long-lasting separation between the worm zone and the very bottom of the trench. If you happen to have a lot of wood chips, don’t hesitate to make this layer a few inches deep or more. The cardboard won’t last nearly as long, but it can end up becoming a highly valuable worm habitat over time.
Next up, we added a layer of aged, bedded horse manure - a fantastic material for these types of systems if you have good access to some.
Then it was a nice thick layer of the grass mats we used for trench #1 (this was grass that had grown on top of an old greenhouse floor sheet, so it was mostly grass and roots with very little dirt). Just a friendly reminder that you should keep these types of wastes fairly well buried, so they don’t start growing and take over the trench.
Next it was time to add our Red Worms - once again in the form of old, worm-rich pig manure.
Since they were being added with their habitat, we made sure to distribute them all along the length of the trench.
Then, more aged horse manure, because…why not? 🤓
NOTE: It’s important to mention that we watered multiple times as we were layering in materials (the full extent of this is not shown in the photos). This is recommended to ensure a more even distribution of moisture, and is especially valuable in the layers associated with your initial worm zone.
Next we added a layer of hay to serve as a sort of “cover”/separator for the initial worm zone.
Then it was a layer of aged, separated dairy solids…
Another layer of bulky cardboard…
Then more horse manure, one last layer of dairy solids, and finally a thick cover layer of hay. All before giving the system one final watering (just a friendly reminder - we watered multiple times during the set up process for a more even distribution of moisture).
Another nice perk of using straw/hay as cover materials (not mentioned in Part I) is that the light colour and loose structure can really help to keep temperatures cooler in the upper layers of the trench during stretches of hot summer weather.
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Trench #2 At a Glance
Differences from Trench #1
- Shallower (more realistic depth for the average home vermicomposter).
- Simpler false bottom, including a lot of cardboard (a material most people have good access to).
- Attempt to use machinery to help with digging (#fail).
Similarities with Trench #1
- 3-zone construction: false bottom / worm zone / cover bedding.
- Some woody stuff in false bottom.
- Alternating layers of different materials - often brown-green-brown-green (but not always).
- Worms added as worm-rich material - lower down in trench.
- Watered multiple times (not just at end).
- Taking advantage of materials readily available.
Once again, just a friendly reminder that both our trenches were set up in a way to best showcase the possibilities for building a system like this! A typical backyard trench could be much simpler - smaller, shallower, fewer materials etc - than ours and still be very effective.
Ongoing Trench Maintenance
Be prepared - vermicomposting trenches can be surprisingly effective waste-processing systems!
With more processing power comes greater responsibility! 😄
When you are using an above-ground system, some neglect won’t likely be as noticeable as it is in a vermi-trench. Leaving one of these systems for too long without adding more materials can potentially leave you with a semi-sunken system - AKA a potential injury-hazard.
Don’t let this concern you too much, though - unlike with a worm bin, there are no strict rules about how to feed a system like this, and “over-feeding” is virtually impossible once the system is up and running (during the set up process, adding lots of rich wastes can lead to quite a bit of microbial heating).
Pretty much any bulky yard wastes or other (compost-friendly) organic matter you can get your hands on can be added to your trench.
During a typical growing season, some readily available options (for most people) are grass clippings and weeds. During the fall, leaves and garden wastes can be an excellent choice.
Trench Moisture Management
Unless you’re dealing with a very hot, dry summer, and aren’t adding water-rich food materials, your trench should remain quite damp down below. One of the great features of these sorts of in-ground systems is their ability to soak up and retain moisture. That being said, if you are growing plants next to your trenches, you will likely have a much more challenging time keeping the systems fully hydrated, especially with really demanding plants during drier stretches of the summer. We recommend adding plenty of water-rich fruit/veggie wastes (always make sure they are buried well), and watering your trench any time you water your plants.
“Harvesting” a Vermi-Trench
Yet another great feature of vermicomposting trenches (and other in-ground systems) is that they can be as low-maintenance as you want them to be. Unlike a more typical worm composting system, there really isn’t any need to ever harvest the compost produced. Simply continue to use them until the level of “finished” material is up to the soil surface (or even above it if you don’t mind ending up with windrows) and then start up new trenches in another location. This can be a fantastic way to boost the overall soil fertility of your property.
If you do wish to clear out a trench (perhaps due to limited space, or to avoid the labour of digging new ones), we recommend doing so every 2 or 3 seasons, ideally early in the spring so you can get new systems set up well ahead of your seasonal planting. The compost excavated won’t be the same as the potent vermicast you harvest from a regular worm bin, but it is still amazing stuff that can be used in a wide variety of ways.
Common Trench-Related Questions
Can I use regular soil worms (do I actually need to add composting worms)?
Composting worms aren’t mandatory, but they will definitely help to speed up the composting process. Certain types of regular soil worms will still move in (or close by) and help out, but if you simply leave the trench as-is (no composting worms), you may find that the level of material doesn’t go down nearly as quickly.
Won’t the worms escape from a trench?
It’s natural to wonder this based on the level of confinement a regular worm bin provides, but one of the key fundamentals of outdoor vermicomposting is that when you provide the worms with a favourable habitat and food supply, they will be happy to stay put. Remember, Red Wigglers (and other composting species) are specialized earthworms adapted for life in environments with rich deposits of organic matter. Typical gardens and lawns will likely seem like a barren wasteland in comparison to your trench! 😉
Won’t trenches attract wildlife?
The short answer is “it depends”. Some very important considerations include: 1) your location, and 2) the types of waste materials you are adding to your trenches.
If you live in a fairly remote location with lots of local wildlife, you may want to avoid adding any of the more typical “kitchen wastes”, since these will likely have a greater potential of attracting animals. Wastes like manures, grass clippings, weeds and leaves (along others) shouldn’t cause issues at all.
Regardless of your location, it’s always important to bury food wastes well down in the system, making sure to cover your deposits with plenty of bedding and (ideally) living materials.
This seems like a lot of work - what are good trench alternatives?
Firstly, just a friendly reminder that a basic backyard trench could be set up much more easily than the trenches featured in these articles! That said, there are definitely some other great options! Instead of a trench, you could create a simple pit system. For added protection, you might consider our DIY In-Ground Worm Composter approach. Even a regular backyard composter with a pit down below it can offer a lot more protection for your worms (from both heat and cold) than more typical above-ground options.
Can I set up a trench in the fall or does it need to be in the spring?
There’s really no “bad time” to set up a vermicomposting trench - although your intended use is definitely something to consider. If, for example, you really want to use vermicomposting trenches to add fertility to your veggie garden(s), it will be advantageous to get everything set up before you start planting. Building a trench after your plants are in the ground, and already growing, can result in root damage and also expose the plants to potentially phytotoxic compounds (from early stages of composting).
Circling back to the original question - getting a trench started in the fall offers its own advantages. There is often a bounty of available waste materials available, and the system can slowly work away over the winter and early spring, leaving it in even better shape for the growing season!
Hybrid (Little to No Digging) Trenches
In some locations, due to very shallow soils (e.g. over bedrock) or no soil at all (e.g. on a concrete or asphalt pad), building a more typical trench won’t be possible. The good news is that it is still possible to create a system with protective attributes that are similar to an in-ground system.
On the more basic end of the spectrum, you have access to a lot of top soil, and don’t mind making a bit of a “mess”, you could simply lay down a really thick layer of soil and dig your trench(es) directly into it.
Taking things up a notch, using actual walls for your trenches can be a great way to provide additional protection. Various types of bricks, construction blocks, or heavy wooden beams can work fairly well, but straw/hay bales would likely offer the best protection.
The downside, of course, is that they will break down over time - but the bonus is that you’ll end up with lots of beautiful, rotten straw/hay you can add to your systems.
Assuming you have access to at least a modest supply of soil, actually mounding it up around the perimeter of your walls can be a great way to boost your level of insulation as well.
Final Thoughts
Vermicomposting trenches are a somewhat under-the-radar type of worm composting system; one that can offer a lot of amazing benefits! They can be pretty labour intensive if you want to get really serious with them, but even very simple trench systems can help you take your outdoor vermicomposting efforts up a notch!
We encourage everyone to give this method a try, and be sure to let us know how it works for you!
Helpful Related Resources
Vermicomposting Trenches - Part I
DIY In-Ground Worm Composter
The Plastia In-Ground Worm Composter
Bokashi - Phase II Turning Your Pre-Compost Into Beautiful Black Gold!
Can I Add Red Wigglers to My Garden?
Outdoor Vermicomposting 101
Living Materials
Bedding - The Most Important Material in Your Worm Bin?
Recommended Products
Red Wigglers
Worm Starter Kit
Worm Rake
pH Buffer Grit
BioChar
EM