Two years ago my area's community garden tried an experiment using the crystals. So this is my only
experience with them. Thus I can't say anything about their safety or toxicity.
25-30 lbs of dry crystals were were soaked in water until they could absorb no more water. They were then spread a generous 1 inch thick in an area of the garden used to grow sweet potatoes. They were immediately tilled into the top few inches of soil, cuttings planted, and the area mulched with 2 inches of the county mulch (predominately ground coconut tree trimmings). Half the bed was planted using rooted cuttings and the rest using fresh cut, non-rooted cuttings. Since there were only
enough crystals to do part of the sweet potato area, fresh cuttings were planted in the rest of the untreated garden beds.
Truthfully this wasn't an actual experiment. It was simply that the community garden got a donation of the crystals and decided to use them in the driest part of their garden, which was the sweet potato area. The hope was that they wouldn't have to drag hoses over there in order to water it.
The gardeners saw no improvement in soil moisture after the first week or so. In this department, the 1 inch application of wet crystals made no difference. Perhaps the application wasn't enough to make a difference? But they did see that the non-rooted cuttings were slower to develop
roots in the treated beds. It was easy to see the difference because the plants didn't look as green nor as robust. This was just opposite of what everyone thought would happen and had been told to expect.
When the sweet potatoes were harvested I saw no evidence of the crystals. I actually looked for them because I was curious. I used a magnifying glass and couldn't pick them out. And I mixed handfuls of soil in water hoping to separate crystal remnants out but still saw nothing. So in 5 months, I could not find any evidence of individual crystals.
As far as I'm concerned, I'm not impressed with these crystals. They are expensive and didn't give the results we had been told they would give. And besides, when they breakdown in the garden soil, what chemicals do they leave behind? Do plants take up those chemicals? No one could give us an
answer backed by facts.
Has anyone else used these crystals and had difference results? I'm curious. Not that I intend to start using them myself. I'm going more and more down the
permaculture road, and I don't see these as being part of my permaculture/low input/low impact homestead plan.