Diatomaceous Earth as a seed starting medium

[RayR]

This experiment started in January when I was wondering how Diatomaceous Earth would work as a seed starting medium. I know that DE is used by some folks in hydroponics as a growing medium, it is also used by some folks in Bonsai, and studies have been done using DE as a soil amendment, but I’ve never ran across anyone who has used it as a seed starting medium. So my curiosity forced me to try it. I had some Blue Ribbon D.E. Premium Cat Litter manufactured by the Moltan Company which I have used as a potting soil amendment, so I had something to start with. From my research on DE I found that the PH of DE can vary depending on where it is mined, so I did a PH test with my digital PH meter and the Moltan product came in at a PH of 6.8 which was perfect, the same as a standard peat based seed starting mix. My first experiment was with Llia Onion seed and the results were very impressive, I grew some very healthy onion seedlings with no problem.
My second experiment came in mid-March with tomato seeds. I found that Moltan makes the same DE product sold as an oil absorbent called UltraSorb which I found right down the street at the local AutoZone in a 15lb bag for $5.99. The only difference between UltraSorb and the kitty litter was the granule size, the UltraSorb is a much less coarse granulation (more like coarse sand), which was easier to work with.

I seeded 24 Brandywine and 24 Black Krim, half in Jiffy Seed Starting Mix and half in DE.They were bottom watered with distilled water, put on the heat mat under lights and given no nutrients until they developed their first true leaves. The germination rate was exactly the same. Here is what they looked like today. See any difference?