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Re: Deformed growth on Hygros
> [is Jim Kelly's] CEC value stated for "laterite" (4) is a true
> value, representative of all laterites, or if it was an average, much like the
> average content of iron in soil has a value but was shown to be a relatively
> useless measure since the range of iron content in soil was quite large.
Jim gave values for Al, Fe oxides (the primary constituents of "pure"
laterite), presumably fine textured as the other materials. Laterite is
a mixture of materials and the CEC is extremely dependent upon the
texture of the material. I don't know if it's adequate or not. I only
know how it ranks comparatively. I think laterite has been demonstrated
as useful in the context of the Dupla straegy; my guess is that it has
something to do with iron, phosphate sequestration and probably CEC too.
Anything is better than sand. It's a complicated subject; I think the
CEC thing may be only a single facet of the whole thing. How about
toxicity from metals? how about humic acids from peat? I think that's
why Dupla went with laterite. Maybe that wanted to use clay initially
but had toxicity problems. Lateritic clay would be the next best thing
without introducing organic systems to the equation. If you start mixing
humus, peat, soil etc with laterite, why bother with the laterite?
Laterite works only because it is part of the whole Dupla system. If
your goal is to avoid the commercial approach using materials at hand
and a minimum of test kits, the approach will be different. It's an
apples and oranges thing.
> From: "Bryan Olynyk" <ots at shaw_wave.ca>
> Subject: Deformed growth on Hygros
My guess is that the vermiculite may be absorbing a lot of your calcium
and maybe its a calcium shortage. After a while the vermiculite will be
saturated with calcium cations. See what a spoon of CaCO3 does once a
week mixed with water for about 2 weeks. TMG probably doesn't have
enough K at a guess and this cation can also be absorbed by the
vermiculite. I had similar problems with Ca shortage by absorption with
peat. That's my theory; extra Ca for a while seems to have cured it.