> Diatomaceous earth looks like crushed limestone but isn't. You may find
> it useful nonetheless.
>
> Diatomaceous earth is composed of the silica skeletons of diatoms. For
> those unfamiliar with the product, it can be found naturally as clay-like
> or rock-like forms. The clay-like form is finely powdered and is used
> both as a polishing agent and as a filter medium.
>
> The rock-like form is crushed and sold both as kitty litter and as an oil
> absorbent for garage use. One common name is oil-dri.
>
> Diatomaceous earth has lots of surface area, like zeolite clays. It is
> therefore great for adsorbing other materials, buffering variations in
> nutrients and PH. When mined, it has rather a lot of trace mineral ions
> already adsorbed so it is often used as a trace mineral amendment.
>
> It holds water well but also passes air freely. It shares that
> characteristic with the open-pore forms of agricultural pumice.
>
> I use it in place of pearlite. It is at least as good for encouraging
> drainage but doesn't float out the way pearlite does. Some hydroponic
> growers use it exclusively. The oil-dri/kitty litter packaging is most
> availabe but must be sifted to remove the largest and smallest particles.
>
> It is a great equalizer. A recent edition of the CSSA journal reported
> cacti and tender herbs growing close together in a high rainfall area
> rooted only in diatomaceous earth. The drainage and porosity kept the
> cactus roots from rotting while the water holding ability kept the herbs
> from drying. The mineral holding ability prevented all nutrients from
> being washed away. Neat stuff!
>
> Bob Cruder - bcruder@miaco.com
>