Questions from Diego:
I just moved in to a house with an untreated clay soil yard. I’m modifying it and I already have the Composting Trench ready for the worms.
Yet, as I have some grass clippings laying around the Trench, will the worms get out of the Trench to feed them elsewhere?
I’m going to buy 100 worms for a 3 foot deep 4 square meter trench, would those 100 worms be enough to give birth to more worms within that space?
For most vermicomposting trenches I would recommend Red Worms (Eisenia fetida/andrei). They are very versatile (tolerant of a wide range of conditions, easy to work with etc), and well-suited for composting environments. In other words, they are going to get the job done – but will only tend to concentrate in areas where there are very rich organic waste deposits. You might find some under old heaps of rotten grass clippings (etc), but the vast majority of them will stay in your trench, assuming you continue to add food for them.
One thing I should mention is that it is important to treat your vermicomposting trench the same way you would treat a vermicomposting bin. You should have plenty of “bedding” types of materials, and ideally some typical kitchen scraps – NOT just yard wastes. You mentioned having your composting trench “ready for the worms” so perhaps you have already taken this into consideration.
As for the number of worms to start with, I actually think it is an excellent idea to start with a smaller number (ideally, in the form of worm-rich material from an existing system) rather than trying to add the “perfect” quantity based on the size of your system. This way you can see if they are going to thrive. And yes, if that is the case, they will certainly increase in number (likely very quickly) so as to take advantage of the available resources.
Just make sure the worms have a “safe zone” to start out in – this way if conditions aren’t yet favorable in the trench, they can just stay where they are until everything mellows out some more.
Hope this helps!
P.S. For others reading this, there are quite a few other Vermicomposting Trench posts you can access from the “Hot Topics” page.