[permaculture] rock dust - is it really necessary?

Keith Johnson keithdj at mindspring.com
Thu Feb 19 17:00:04 EST 2009

The question is less about whether it's necessary and more about if it's 
available as a byproduct of ongoing processes whether it could be 
utilized to advantage and turned from a waste to a resource.

My primary exemplar of the usefulness of rockdusts, besides my 25 year 
history with it, is Bob Canard, grower for Alice Waters, et. al.

Solubility is of course tied to soil life, but simple tests show that it 
is used by plants even in relatively lifeless conditions. The addition 
of *very fine* rockdust minerals to pure lifeless sand will demonstrate 
its availability to plants by the quality and quantity of root growth 
clearly visible in contrast to the same plants without. I urge you to 
put this to the test and see for yourself. Belief is not sufficient.

I've studied Ingham's work fairly thoroughly (and I admire her 
tremendously) and have not encountered that particular claim ("that all 
soils on earth have plenty of all necessary nutrients"). It sounds like 
one of those absolutist statements for which there are usually 
exceptions. If you can cite the location of that claim and it's 
accompanying proof, I'd like to read it.

I would further suggest that soil organisms respond quite directly and 
immediately with the introduction of rock dusts. If life, macro and 
micro, increases by the use of the material, then the further 
development of soil life is also thus enhanced, which is to say that the 
soil biota's capacity to unlock nutrients IS increased. The quality of 
compost that includes rock dusts is readily observable in side by side 
growth comparisons and I have OBSERVED it repeatedly. I do not know if 
Elaine has compared the character or quality of soil life in 
mineral-enhanced composts. I only have my direct experience. If anyone 
knows of such microbiological assays I would love to see them.

Jordan Fink wrote:
> i have to ask the question here- is rock dust really necessary for any
> permaculture site.
> Dr. Elaine Ingham of Soil Food Web is saying that the evidence suggests
> that all soils on earth have plenty of all necessary nutrients to grow
> healthy food. Many soils, however, don't have a healthy soil food web
> which means that all that nutrion is biologically unavailable. The
> application of organic fertilizers and rock dusts just adds a little bit
> more soluble nutrients but doesn't improve the soil biota's own capacity
> to unlock the resourses already available.
> A few well-designed applications of compost tea will have better
> results, cost far far less and you don't have to justify supporting
> dredging and mining.


Keith Johnson
"Be fruitful and mulch apply."
Permaculture Activist Magazine
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