Let's talk soil amendments, e.g. pumice, pine fines
After reading various discussions on the soil & cactus forums, I got very interested in pumice as an amendment to heavy clay soil.
Never could locate it in my area, even as DryStall horse bedding. Where pumice is locally available--CA & AZ it's widely used.
So, after studying the forums, I started experimenting with calcined products--calcined clay kitty litter, Napa #8822 Floor Dry (calcined diatomite), Lava Sand--fine textured red lava rock.
As I understand it, the calcined products are fired so that the clay doesn't break down to silt.
In my casual experience, all of these work well to improve the tilth & drainage of the heavy clay I tried them in. I was dealing with dense black "gumbo" clay of the TX gulf coast.
Another place they have been beneficial is in cutting rooting media. I noticed that Vintage Gardens & several other places send their roses rooted in a media heavy on the red lava pieces (up to maybe 1/4" size), & perlite. I don't know if the other component is peat or coir--it is dark & fine. I've been using coir & it keeps the media moist but not so saturated as to cause rot.
So it's also nice to learn (Strawberryhill, Garden tips thread) that the calcined products & lava sand also have nutritive value to plants besides improving soil tilth & drainage. It seems that even the silica in them improves stem strength in plants & there are some interesting anecdotal & experimental data to support this that Straw has posted on the garden tips thread. Lava sand is available in my area, not too expensive, Napa #8822 is $6.50 per 20b bag, various calcined clay kitty litters for about that price.
Another well-liked amendment that it took a while to locate in affordable amounts was pine fines--used in all sorts of mixes from Al's Gritty Mix to citrus potting (5:1:1 mix) etc. I never could locate it in affordable quantities & was sifting shredded bark for awhile.
But Lowe's carries a mix called HapiGro landscape mix & it looks to be 90% pine fines, very nice texture, flakes about 1/4". Quite affordable, a huge bag runs~$5.00
I'm finding coir bricks locally for about $6-$6.50 per brick.
Now I'm dealing with caliche--a dense calcium carbonate common in desert soils. But it appears that coir, pine fines & lava/calcined clay products may be useful for soil mixes in this zone, also, both to improve texture & to counter the alkaline water & desert soil. Ironically, gypsum, too. The calcium of caliche isn't chemically available to plants to adsorb & the alkaline soil & water benefit also from the sulfur available from calcium sulfate. Gypsum is pretty reasonable, around $8.00/40lbs.
So what amendments are you finding useful & where the heck have you found them?