Hi all,
If I was to add a small pea size ball of red clay under a plant, would it be able to obtain iron from it?
It depends upon the level of oxygenation of the substrate, if the substrate is all aerobic, then the iron (Fe) will remain as iron III (hydr)oxides, and never become available.
If the substrate contains anaerobic areas the reservoir of iron in the clay balls (you know they contain iron, they are red) will become plant available.
Because clays have small particle size, it is likely that some iron ions will become available in most substrates.
If your tank has very hard water the problem is that the iron ions will rapidly form other insoluble compounds, if you have soft water and low pH, they will remain plant available.
You can tell the iron content of the clay iron III oxide (
<"rust">) in the clay by the colour. It is the same reason bricks are red, all the iron is oxidised and unavailable. If you take a green ferrous (Fe II)
<"gley soil"> and bake it, it will change colour from green to red (ferric - Fe III).
<"Lateritic soils"> form in tropical areas, under conditions of high rainfall, because all the soluble cations are leached, leaving only the insoluble aluminum (Al) and iron oxides behind. They will remain in this state almost eternally if conditions remain aerobic.
cheers Darrel