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How To Build a Worm Tunnel In-ground Worm Farm

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How could composting be made easier? By not ever having to turn the compost and not having to move the compost into your garden, that’s how!

You can get Nature to do even more of the work with a Worm Tunnel, an in-ground worm farm that’s a cross between a small compost bin and a worm farm that sits in your garden (in the soil). You just throw in your fruit and vegetable scraps from the kitchen and that’s it, the worms that live in the soil in your garden do the rest. The worm castings and the liquid from the worm farm all go straight into the soil where they are immediately available to plants and trees.

Worm tunnels are cheap and easy to make, and can be made from recycled plastic plant pots. They can process the same materials as any other worm farm, and best of all, they can be made in a few minutes, as explained in the instructions below.

Construction

To construct a worm tunnel, you’ll need the following materials:

You’ll need the following tools:

Step 1.
Take the plastic pot, drill holes in the side

I prefer to use make large 1” (25mm) holes with a holesaw as I drill less holes that way.

Here’s what a holesaw looks like in case you’re wondering!

Step 2.
Cut off the bottom of the pot

I just used some heavy duty scissors/shears to do this, use whatever works easily.

Step 3.
Find a plastic pot watering tray is large enough to fit over the top of the pot as a lid

Step 4.
Test fit the lid to make sure it fits – it’s now ready to go into the ground!

Step 5.
Dig the hole, and sit the worm tunnel in the soil, fill around the sides with soil.

NOTE: Choose an accessible location, near a path or walkway, as you’re more likely to put your kitchen scraps in a worm tunnel if you can get to it easily or pass along that way often (This fits in with the Permaculture design principle of Relative Location)!

Step 6.
Get some compost from your compost bin an pour it into the bottom of the worm tunnel.

This will introduce beneficial soil organisms that will assist with the composting process.

Step 7.
Add fruit and vegetable scraps and other materials that you would normally put into a worm farm (see worm farming article for details).

Step 8.
Place a cover over the food scraps to create a dark, damp environment favourable to earthworms.

This cover (worm blanket) is simply made out of a folded piece of damp newspaper or a scrap of damp hessian sack that is placed over the top of everything.

Whenever you add new material, place it under the newspaper or hessian worm blanket cover.
(TIP: I normally leave a short stick beside the worm tunnel which I use to lift up the newspaper so I don’t get my hands dirty!)

Step 9.
Put the lid on the worm tunnel.

It’s very discrete and easy to disguise or hide if necessary.

To stop the lid blowing off in the wind or to prevent animals getting inside put something heavy on top (such as a rock)!

Step 10.
All Finished! Now just sit back and let the earthworms do the work.

Use and Maintenance

Within a few weeks earthworms will move in from the soil and start feasting on the food scraps in your worm tunnel.


Inside an established worm tunnel, lots of earthworm activity!

Despite the size, you won’t fill up a worm tunnel in a hurry! A 300mm (12”) wide standard pot has a volume of approximately 12L (over 3 US gallons) so there’s a bit of space in there.

As you add material, it will pile up initially , then break down and reduce in volume. It will take a while before the whole tunnel is filled with worm castings, around two years in fact, because most of the volume of fruit and vegies is actually water!

If you’re generating a lot of kitchen scraps, you make a few worm tunnels and install them all around the garden.

When the worm tunnel fills to the top with worm castings, just lift the whole thing out of the ground, leaving the nutrient rich worm castings behind in the soil of course, and move the worm tunnel to a new spot in the garden and start again!

Design Considerations

The original worm tunnel concept can be credited to Linda Woodrow, permaculture writer/experimenter from NSW, Australia and author of The Permaculture Home Garden. Her idea was first published in an article in Australian Organic Gardener in 2000. As she has indicated, the idea has grown and evolved since then!

The design shown above is my own design, and will work very well. You can also use various other containers to build a worm tunnel in-ground worm farm.

As long as you stick to the basic design concept, which is:

-then it should work just fine, so feel free to experiment.

My design is very utilitarian and functional because that’s what I prefer, but if you want something fancier looking, then feel free to let your creativity run riot.

Here’s a worm tunnel design in a friend’s garden that involves the use of recycled materials and looks rather ornamental.

What looks like a small decorative pot with lid sitting under a small citrus tree…

Is really the top of a bottomless container brimming with earthworm activity!

You can make your worm tunnel bigger than the one in my design, but keep in mind that if you use a very tall container, you’ll have to dig a very deep hole, and that may prove very discouraging or even impossible if you hit solid clay! You also need to be able to pull it out of the ground once it is full too!

My recommendation is to start with the size I’ve recommended, I’ve chosen that size because it’s quite manageable, and if you succeed and you’re confident you can manage it, then by all means go bigger.

In Conclusion

Worm tunnel in-ground worm farms are a very energy efficient solution to recycling fruit and vegetable kitchen scraps. They really tie in well with sustainable gardening and Permaculture principles on several levels.

It’s definitely worthwhile spending a few minutes to build a worm tunnel, you’ll be glad you did, and so will the earthworms in your garden!

If you’d like to learn more about worm farming, please check out the following articles:

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