After a new bin has been running for a few weeks, you'll see the
bedding becoming darker and will spot individual worm casts. Even
though food is steadily added, the bedding will gradually vanish.
Extensive decomposition of the bedding by other small soil animals
and microorganisms begins to be significant.
As worm casts become a larger proportion of the bin, conditions
deteriorate for the worms. Eventually the worms suffer and their
number and activity begins to drop off. Differences in bedding,
temperature, moisture, and the composition of your kitchen's garbage
will control how long it takes but eventually you must separate the
worms from their castings and put them into fresh bedding. If you're
using vermicomposting year-round, it probably will be necessary to
regenerate the box about once every four months.
There are a number of methods for separating redworms from their
castings.
_Hand sorting_ works well after a worm box has first been allowed to
run down a bit. The worms are not fed until almost all their food
has been consumed and they are living in nearly pure castings. Then
lay out a thick sheet of plastic at least four feet square on the
ground, floor, or on a table and dump the contents of the worm box
on it.
Make six to nine cone-shaped piles. You'll see worms all over. If
you're working inside, make sure there is bright light in the room.
The worms will move into the center of each pile. Wait five minutes
or so and then delicately scrape off the surface of each conical
heap, one after another. By the time you finish with the last pile
the worms will have retreated further and you can begin with the
first heap again.
You repeat this procedure, gradually scraping away casts until there
is not much left of the conical heaps. In a surprisingly short time,
the worms will all be squirming in the center of a small pile of
castings. There is no need to completely separate the worms from all
the castings. You can now gather up the worms and place them in
fresh bedding to start anew without further inconvenience for
another four months. Use the vermicompost on house plants, in the
garden, or save it for later.
Hand sorting is particularly useful if you want to give a few pounds
of redworms to a friend.
_Dividing the box_ is another, simpler method. You simply remove
about two-thirds of the box's contents and spread it on the garden.
Then refill the box with fresh bedding and distribute the remaining
worms, castings, and food still in the box. Plenty of worms and egg
cocoons will remain to populate the box. The worms that you dumped
on the garden will probably not survive there.
A better method of dividing a box prevents wasting so many worms.
All of the box's contents are pushed to one side, leaving one-third
to one-half of the box empty. New bedding and fresh food are put on
the "new" side. No food is given to the "old" side for a month or
so. By that time virtually all the worms will have migrated to the
"new" side. Then the "old" side may be emptied and refilled with
fresh bedding.
People in the North may want to use a worm box primarily in winter
when other composting methods are inconvenient or impossible. In
this case, start feeding the bin heavily from fall through spring
and then let it run without much new food until mid-summer. By that
time there will be only a few worms left alive in a box of castings.
The worms may then be separated from their castings, the box
recharged with bedding and the remaining worms can be fed just
enough to increase rapidly so that by autumn there will again be
enough to eat all your winter garbage.