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  • From: Keith Johnson <keithdj@mindspring.com>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Rock Dust
  • Date: Sat, 02 Apr 2005 18:04:59 -0500

I live in a spot (mountainous west North Carolina) that 90 years ago lost more than half of its topsoils to erosion due to clearcutting, overgrazing, and farming on steep slopes. The average pH is about 4.3. We have sandy red clay soils and decomposing granite in the subsoils. The soils are critically short on calcium and phosphorus but rich in iron and magnesium. Young hardwoods have recovered most of the eroded soils and all our present farmland was under trees until recently. There is very little calcium bearing rock in our subsoils.

We could wait for our deep diving plants to accumulate the goodies but with minerals I can build up a humic "savings account" much faster. The finer the material, the less I need. 50 pounds is enough for about 1/4 Acre. Although we have stockpiled tons of material, it will last us for many years and many acres. Once it is stored in humus it remains for years and years. For trace minerals I use seaweed, urine, pond weeds and algae.

Rock minerals can help me raise the pH, and due to the, ideally, small size of the particles the overall surface area available for microbes to grab on to is very high. Compare a the surface area on a rock the size of your fist and the same rock powdered. Bio-availability is enhanced by powdering. Once the minerals are cycled into plants they remain quickly available by decomposition. A little manure mixed with the minerals gets it sizzling with the next rain or watering.

A simple test is to plant two rows of radishes (the little ones, not daikon) and sprinkle rock dust on one row. In about three weeks time dig up some of the radishes in each row and compare the fine root hairs. Consistently the dusted plants will have many more short feeder roots which hold onto more soil and the undusted plants will have longer, "seeking roots" and fewer fine feeder roots and the soil falls off the roots. The dusted plants get a lot of what they need without having to expend energy sending roots to distant minerals. I have often observed a change in the color of plants, brassicas especially, to a darker bluer green within 24 hours of dust application. Also "tear strength" of the leaf increases and I have observed increased frost and pest resistance. Brix readings also tend to rise after mineral application. I also notice a remarkable increase in earthworm populations.

I would have to wait 3-5 years to be able to grow good chenopods if I let the subsoil miners take their time but with a little dust, I can have beautiful beets and chard the first year after the trees are removed.

Eugene F. Monaco wrote:

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. Let the local
plants and critters do the work. Am I being to idealistic? Or maybe it has
simply to do with the time dimension. Comments?

Gene Monaco


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--
Keith Johnson
Permaculture Activist Magazine
PO Box 1209
Black Mountain, NC 28711
(828)669-6336

also Patterns for Abundance Design & Consulting
Culture's Edge at Earthaven Ecovillage
http://www.permacultureactivist.net
http://www.earthaven.org
http://www.bioregionalcongress.org





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