[permaculture] Rock Dust

Marimike6 at cs.com Marimike6 at cs.com
Sat Apr 2 15:33:11 EST 2005


Gene--  Your point sounds perfectly reasonable, but soil profiles vary 
immensely depending on your location.

<< I've never used rock dust but have a question from a skeptical 
perspective.
I don't doubt that it can be good in the short term much the same as
fertilizer can be good in the short term, but does it go beyond there? My
question has to do with the natural processes that are being ignored.
It seems logical that the deep-root plants (think dikon radish) can mine the
minerals from the rocks below and bring them to the surface in a
bio-available form, which, subsequently, can be available to other plants as
the soil is built organically. No place on earth doesn't have rocks under
the soil. So all this stuff about soils being depleted -- a la Dead
Doctor's Don't Lie -- could be remedied with soil building. No? Why not
put your energy into building soil with natural systems rather than hauling
in tons of crushed rock from a quarry some place offsite. >>

In my neighborhood there's fossil beach sand going down 200 feet or more 
before you hit bedrock. I'd have to ask a well driller what the profile actually 
was. I know there's layers of subsurface streams down there. My well is (I 
think) 180 feet down.

In the Mississippi Basin, soil depths go down 3-4,000 feet before you hit 
bedrock. Obviously the burden of alluvium compacts and weighs heavily on the 
lower layers, so you could at some point certainly call it rock. But I think the 
point is that each site is different. My profile (deep sand and moderate rains) 
leaches the mineral and organic content, so they have to constantly be 
replenished. It's what you would call a poor soil. Elsewhere your daikons might well 
dredge up nutrients beyond the reach of shallower root systems. I'd contact 
the County Ag Extension man and see what he had to say.



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