I’m moving a bunch of my nursery stock trees from containers --> grow bags --> raised beds today. Some of them (all bald cypresses) have been in 100% diatomaceous earth for ~18 months.
The DE was thoroughly screened, then thoroughly rinsed, before the trees went in. I live in Louisiana on the edge of zones 9a/9b; this substrate has experienced MAYBE one night below 32F. We get a lot of rain and the humidity is roughly 120% for eight months of the year.
Here’s what the bottoms of those containers and trees looked like today.
Some of that could be dust that I failed to wash out… but I think at least some of it is DE particles that have broken down.
Data for your consideration.
(I have this suspicion that @BillsBayou might have additional data or insight.)