Calcined DE used as soil amendment - safe for earthworms?
Calcined DE has been heat treated to stabilize it and is used in pool filters - but also as a soil amendment for golf courses and sports fields. One such brand is "Axis".
It is also increasingly being touted as a soil amendment/container soil component for gardeners, usually the form being recommended is NAPA Oil Dry 8822.
However there are multiple warnings across the Internet - for whatever that is worth - NOT to use calcined DE (usually referred to as "pool" DE) for a soil amendment as it is harmful to earthworms.
Give me the skinny - can I dump my spent container medium that has calcined DE in it into my compost, and thence into my garden without endangering my earthworms? Or is calcined DE unsafe at any depth for the earthworm population?
I have already ceased to use calcined DE as a component of container mixes due to its extremely poor performance, but I have quite a bit of it leftover in a "gritty" mix. If it is harmful to earthworms, then into the trash it goes. If not - into the compost, as other components of the mix are still of some use.
We think you can safely put your spent container medium in your compost, because it is calcined, i.e. heated, which makes it less abrasive. It should not damage arthropods in your compost.