Re:earthworm castings

Stephen Pushak worte Oct. 30 re earthworm castings:

>I don't think we will find a really big difference between good quality
>black loam and earthworm derived humus aside from higher proportions of
>sand or clay in the former which may not matter. Sometimes it's just
>hard to find black loam. The dirt available here in Vancouver is pretty
>sandy or clay with low humus. That's why I didn't use it.
>The point of using earthworm castings is to provide a high quality,
>fully composted humus. It would be useful for Aponogetons, Ludwigia
>and other species which tolerate a rich substrate. If used in moderation
>it would also do well for a general purpose substrate and would be very
>similar to plain dirt or topsoil. It has the (possible) advantage over
>potting soil in that it does not contain uncomposted organics such as
>peat. Of course, Neil Frank is using a peat and vermiculite substrate with
>good success. Neil, is that substrate designed for a specific type of
>plants or kind of general purpose? What was the composition again? I
>also recall you mentioning that mud substrates are very commonly used
>by the academic types for research on aquatic plants. In your opinion,
>are these soil based substrates trickier? Karen, are Crypts generally
>lovers of rich, muddy substrates too?
If the soil in Vancouver is low in humus, you can improve it by adding peat
or dried cow manure or dried leaves and composting it in a covered, plastic
storage box for about three weeks at room temperatures.  That is all the
time it takes to break down all but very resistant organic matter.  What is
left will not harm plant roots because of too high a biological oxygen
demand.  I do not believe that all the organic matter has to be composted
so long that the soil has the appearance of fine black loam without any
visible remanents of leaves, stems or other plant parts.  Three weeks is
plenty long enough in my experience.

The majority of aquatic plants, in my experience do well in soils rich in
organic matter.  Their roots have large air channels through which oxygen
diffuses at a rate 100,000 times faster than it does in water. Crypts
especially like lots of organic matter in the soil.  I have seen a number
of people report very good growth with peat or potting soil.  Peat actually
is partially composted, and the potting soils I see are mostly partially
composted tree bark chips, which decompose very slowly. I would not want to
grow my plants in straight peat or potting soil because I want real topsoil
present too, primarily because of its iron content.  I usually throw in
some broken up egg shells to provide calcium and keep the pH from getting
too low.  I assume that most underwater soils have a lot of old snail
shells present.  Some of the plants that don't like a lot of organic matter
are Anubias species, Microsorium, and probably some of the Aponogetons.

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174