I guess I'm supposed to answer these since no one else did, and I initiated the discussion too, didn't I.
Originally Posted by steven
1. What risks do you see in using the red clay?
2. Why the topsoil rather than the vermiculite? The vermiculite gives the mix a very "light and airy" texture, presumably making it very easy for the plants to grow roots in.
Please don't think I'm questioning your ideas, I'm just always looking for new perspectives.
First let me say, PLEASE question ideas, no one has a good idea that is so well thought out that someone asking the tough questions would be wasting their time.
1) These are some possible
problems, not probable
problems, pestisides and herbicides, pollutants, toxic chemicals. Unless you can verify that nothing has come in contact with the clay for a while you have these risks.
I can't verify this with the commercial topsoils I buy, and I didn't verify IRONITE but that's another story, BTW: Thanks Rex.
I would use the red clay, I'd even go collect some if I weren't happy with buying potters red clay. I also wet and dry my soils to try to complete the decompossition of humis which helps wash away pollutants.
2) Mineralized topsoil (MT) is a nutrient milkshake for plants, vermiculite(V) is nothing. MT is a great medium for plant roots, V tries to add something to the medium that isn't needed in an aquatic environment. MT binds to clay particles keeping the clay from going into suspension when you disturb the substrate, and keeping the clay mixed into the substrate where it can adsorb and release nutrients that are 'released' in the substrate from the soil, V can't take up enough of the substrate to do this better than MT.
V floats, yuck.
Beginners, do not use soil, please.