[Terrapreta] USDA organic certification standards

[rukurt at westnet.com.au]

Sean K. Barry wrote:
> Hi Tom,
>
> Sand maybe (to help with drainage)?  Gypsum (calcium sulfate dihydrate), clay, vermiculite, and perlite are all minerals with low solubility and help soil hold water.  Gypsum releases nutrients and improves soil structure.  Vermiculite has high cation exchange capacity.  I believe charcoal is insoluble.  
>
> SKB
>   
Green sand has special properties, not sure what they are. Aparently 
it's not green, basically it's moist sand and clay mixture and used in 
metal casting molds. What it does in gardens I don't know. Just googled it.
Vermiculite and perlite are are both manufactured by heatreating rock. 
Gypsum breaks up clay, clay makes sand less permeable and helps to hold 
water. Yes, charcoal is insoluble, that's why it will sequester carbon, 
but it's porous nature allows it to adsorb and harbour all sorts of things.

Kurt