When it comes to worm composting, the rotating tray method is one with clear logic behind it. Simple enough for nearly anyone to use, thousands of families like ours successfully use systems like these to upcycle their kitchen waste year after year.
Their popularity comes as no surprise. Even moderately priced units come equipped with built-in solutions. They keep away pests, allow for drainage, encourage airflow, and can be used to cure and harvest the worm compost.
That’s not all. Their stackable, perforated layers create a sizeable worm composting set-up in a really small space. For example, in only 18” square, our Worm Factory 360 holds as many as 10,000 worms, and holds up to 6 trays at a time!
That’s really exciting. But numbers like that only happen once you’ve got a whole tower of trays going strong and steady.
So, how do you go from stage one, the first bottom tray, to a fully-rockin’, rotating stack of worms at work?
If you’re curious, you’re not the only one. Lots of readers email us asking how to use the rotating tray method for worm composting. Luckily, It’s pretty simple.
Come on, I’ll walk you right through it.
When is it time to start a new layer?
First things first, right? You don’t want to jump the gun on this one, and I’ll tell you why.
When you establish your very first tray, with a brand new colony, encouraging reproduction is your top priority. The more you can keep worms near each other, the more likely they are to get together and populate that space.
But when it’s time, it’s time. Here are some indicators:
- Population reaches max density.
- Bedding and compost reach the top of the tray.
- You want to quickly expand an already established colony to process more waste.
How do you start the next layer?
Second, and all following layers, are even easier to start than the first.
Remember how you set up your first tray? No? Need a reminder?
Okay, we’ll start here: The second layer starts like the first but without a layer of newspaper to separate the levels.
Then, it’s really all about the bedding. I make bedding like I’m cooking a recipe. Here’s one way I do it, and you can too:
- I start with a huge stainless steel bowl and add soaked, drained, and fluffed shredded paper. (I’ve used coconut coir, leaves, bark, etc.)
- Into that I add torn up egg cartons, to help with airflow and moisture maintenance.
- Then, in go crushed eggshells for grit and minerals, spent coffee grounds (because I have tons), and a generous scoop of the good stuff (finished compost) from tray #1- worms and all.
- I set my ready-and-waiting empty tray atop the original, still allowing for airflow and movement of the worms.
- Into the tray the bedding mixture goes. I like to start with about 2 inches of this “starter” across the bottom, but even a little pile will do.
- To encourage my worms to start their migration, I place feedings only in the newly created tray.
- Then, since new layers are usually sparse and rather exposed, I like to blanket the top with moist cardboard or newspaper. This ensures the humidity stays high and that more worms stay close. Move the first tray’s newspaper ceiling to the second tray on top of the bedding. This will “open the door” to worm travel between layers.
What about rotation?
Rotating your trays happens after you’ve got a full stack piled up. The purpose is to allow each tray to be harvested on a regular basis, maintaining a more healthy environment than one in which compost sits too many months.
The rate at which you rotate will depend on feedings and conditions in your own worm bin. Generally, a mature colony will finish a tray in 3 months or so. And when this happens, that bottom tray needs to find its way out and to the top.
To rotate my trays, I lay my lid upside down on the floor and unstack my tower one tray at a time beside me. Once I reach my treasured bin of finished compost, I set it aside, and rebuild my tower of worms.
Kept in the same order as before, now tray #2 is on the bottom. Without any lid, the #1 tray gets put on the top of the stack. It will stay there exposed just long enough to dry out and get the worms to move down into #4.
Once that bin is cleared out (harvested), where does it go?
Right back on top, with a lid, to await a fresh start.
Which layers get feedings?
Compost worms are simple creatures. They go wherever the food is. So if you want some worms to go live in a new neighborhood (tray #2, 3, 4), put the food there. If you want some to move, but some to stay and finish the work they started down below, go ahead and put food in both places.
As soon as you think a tray is getting close to completion, stop putting food into it. This will help it to start to dry out a bit and encourage worms to evacuate.
How to Get your Worms to Move Out
Most worms don’t mind exploring, especially when something tasty is nearby. But others seem to prefer staying put, in dark, wet, worm-filled places. That sometimes means, getting your worms to scoot takes some extra assistance.
There are a few ways to get this job done:
- By hand
- By lure
- By exposure
To remove your worms by hand is very time consuming and frustrating. It does, however, allow you to get up close and personal with your crew. If you choose this route, be sure to block out a good chunk of time and expect to make a mess. There will be clean up.
Using a lure is more of a hands-off approach. Your best bet? Some kind of melon or squash that’s starting to go bad. Simply irresistible! Whether placed in the tray above or below, the worms will head that way. Withholding a feeding or more before the planned move will draw more worms more quickly.
The last is my favorite, evacuation by exposure. Knowing that worms instinctively slink into the dark when light appears, we can easily get them to move DOWN by applying light from above. Generally, this happens in the open…which then begins to dry out the bedding, forcing worms to seek wetter conditions DOWN BELOW.
So, as a tray comes out of the rotation, it is placed without a lid at the top of the stack. Light and air from above start the migration process. Periodic hand-raking of the top layers loosens what can be either harvested or left to dry further. As top layers are removed, the worms work their way down through the bedding, and eventually into the tray below.
How long does it take worms to move into a newly added tray?
I remember the first time I tried to harvest a tray and needed my worms to move out. I thought it would take a few hours for them to find the food hidden just beyond their tray. Man, was I way off!
I didn’t realize what I was expecting. My worms were livin’ large in gorgeously fine compost. It had just the right moisture content, pH, temperature, and lots of like-minded individuals there too. How was a mere piece of fruit to contend with that?
Needless to say, when I came back a few hours later, I discovered a weak turn-out at cantaloupe corner. I was shocked.
These days, I allow a full tray of finished compost about a week to clear out. I feel as if this “slow” process is a fairly natural way of moving them out while having the added benefit of curing the compost at the same time.
But to answer the question more directly, I can only say that it all depends on the existing conditions and what’s on the other side. Then, on their own, a vast majority may move through as quickly as overnight, while others may linger for weeks.
Do you have any more questions about the tray method of worm composting? Please let us know in the comments section below.
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