permaculture

[Lawrence London <lfljvenaura@gmail.com>]

Rock Dust
http://davesgarden.com/guides/articles/view/727/
Rock Dust… DUH!!
*By Darius Van d'Rhys (darius <http://davesgarden.com/members/darius/>) *

*April 2, 2008*Eons ago the earth had a mantle of rock. Then the glaciers
slowly and inexorably moved and ground the rocks into a thick layer we
called dirt. The dirt supported plant life, which took in the minerals
needed for growth, and gardens were born. Over thousands of years,
essential micronutrients were continually taken up by plants, often to the
point of exhaustion. We as gardeners attempt to add nutrients back to the
soil by means of fertilizers, compost and/or other amendments that we
purchase and apply in vast and expensive quantities. However, those
materials rarely contain all the micronutrients eroded away or taken up by
plants.

*What are Micronutirents?*

“Eight of the seventeen elements essential for plant growth are
micronutrients. On soils deficient in these micronutrients, the application
of small amounts of these nutrients can greatly enhance crop production.
The micronutrients are Boron (B), chlorine (Cl), cobalt (Co), copper (Cu),
iron (Fe), manganese (Mn), molybdenum (Mo) and zinc (Zn). With the
exception of nitrogen, all plant nutrients are of geological origin. Under
natural climatic conditions the physical breakup, chemical weathering and
release of nutrients from minerals is not fast enough to provide the
nutrients for annual crop production.” [1]

There was an area of New Zealand where the sheep were dying for no obvious
reasons – there was plenty of food. Then it was discovered that the soils
were deficient in the element cobalt. It is well known that cobalt is
needed for our immune systems. Another example is provided by E.I. Steifel,
Science, 996, vol. 272, where he showed that the process that accounts for
much of natural nitrogen fixation in soils requires molybdenum. In many
soils adding a trace of Mo would reduce the need for nitrogen fertilizers.
[2]

It has been suggested elsewhere that there are as many as 90 minerals
needed by plants. Minerals are also essential for human health and the
human body utilizes over 80 minerals for maximum function. [3] Because our
plants and soils are so nutrient depleted, even if we eat the healthiest
foods, we are not getting all the minerals we need.

*One Solution*

There is one simple solution: rock dust. Rock dust is generally a
by-product of the gravel industry and is available almost everywhere, often
free for the taking. Rock ‘gravel’ or dust is found in the bottom of creek
beds, and pond settlings. The finer the size, the easier microorganisms can
access the minerals but if the rock dust has been ground into silt, it is
too fine and will merely clog up the pores in the soil.

The use of rock dust is not new. Agricultural research with finely ground
and chemically unprocessed rocks and minerals, based on the concept of
“bread from stones” started in the 19th century by Missoux (1853/54),
Hensel (1890, 1894) and others. The Hardin Brothers in Queensland Australia
have been using rock dust more than 20 years. They have found less
environmental damage, 25% higher yields, 20% increase in growth rates and
80% less fertilizer. [4]

One reason seaweed is so effective in the garden is the high trace mineral
content. Greensand, a common soil amendment, is just dust from sandstone
rock that was deposited in marine environments.

*How does rock dust work best?*

Rock dust is most effective when mixed 50-50 with organic compost and a
handful of soil to add some microorganisms. The microorganisms feed off the
rock dust, taking only the nutrients they need while leaving the remainder
in the sub-soil. The compost provides the medium for the microorganism
growth. Optimally, the rock dust and compost mixture should be incorporated
into the top few inches of soil if possible but may also be spread by
broadcasting or spread by hand if you use a no-till method of gardening.

It is not totally necessary to add the rock dust mixed with compost. The
dust alone may be added and raked in, or tilled in. The addition of compost
just gives the rock dust a head start as food for the microorganisms.

An interesting benefit of adding rock dust is that it will help create more
organic matter, which in turn helps hold the soil in place and conserve
water. Soil erosion is an effect of the shortage of minerals to support the
soil organisms. “That shortage can be made up on any piece of land in the
time it takes to work ground gravel dust into the topsoil. When that is
done, the soil microorganisms begin to multiply and it is they who prevent
soil erosion by granulating the soil and holding it against both wind and
rain." [5]

*What will Rock Dust Do for my Garden?*

Applying rock dust is often called “remineralization” which actually
revitalizes the soil by mimicking the process of glaciiation.

Rock Dust:
Provides slow release of trace minerals
Increases microorganism growth
Builds more soil
Increases nutrition in plants and crops
Cuts the need for chemical fertilizers
Increases water retention in the soil
Increases pest resistance
Increases crop yield
Reports of increased winter hardiness

There is a wonderful photo comparing carrots grown in, and grown without
rock dust here: http://prorev.com/dust.htm. Unfortunately I have not been
able to locate the copyright holder to get permission to use the photo here.

*What Kind and Size Rock Dust and How Much?*

If the mesh that screens the rock dust is of the size “minus 200” (gravel
industry standard nomenclature) it will work in your garden. Masonry sand
and sand made for sand-blasting procedures are too coarse and will not be
as effective in your garden, taking longer to break down. Rock dust from a
gravel pit is usually unscreened but about the right size.

Locally, I have granite dust available from the gravel pits, which is okay
to use but not best. The mixed gravel dust from the local stream beds is
better. A better yet rock dust comes from glacial gravel or volcanic rock
like basalt. Another is montmorillonite. Montmorillonite is a very soft
phyllosilicate mineral that typically forms in microscopic crystals,
forming a clay. It is the main constituent of the volcanic ash weathering
product, bentonite. [6]

An application of 2 tons per acre is the minimum amount, and as much as 20
tons per acre for exceptionally poor, dry soil. Use about 14 pounds of rock
dust per 100 square feet of garden bed (or 5 pounds per square yard). If
this sounds too good to be true, try an experiment at home with potted
plants: take a 6” pot filled with half soil and half peat. Add 3
tablespoons of rock dust. Do another pot just the same but leave out the
rock dust. Put identical plants in both pots, and watch for astonishing
differences!

*Footnotes:*

[1] *Rocks for Crops*, ©Peter van Straaten, used by permission
http://www.uoguelph.ca/~geology/rocks_for_crops/
[2] Aston, Bernard Cracroft
http://rsnz.natlib.govt.nz/volume/rsnz_80/rsnz_80_01_002320.html
[3] http://www.northupfamily.com/Farms/Colloids.htm
[4] W.S. Fyfe, Professor Emeritus, Dept. of Earth Sciences, University of
Western Ontario, London, Ontario, Canada
[5] http://prorev.com/dust.htm
[6]*The Survival of Civilization*, John Hamaker
[7] http://en.wikipedia.org/wiki/Montmorillonite

*Additional information here:*
*Bread from Stones* by Julius Hensel
http://www.amazon.com/Bread-Stones-Acres-U-S-classic/dp/0911311300/ref=pd_bbs_sr_2?ie=UTF8&s=books&qid=1201968923&sr=1-2
http://www.remineralize.org/benefits.php
http://query.nytimes.com/gst/fullpage.html?res=9502E6DB1139F937A15755C0A9629C8B63
http://www.mulchnet.com/Products/rock_dust.htm
http://www.gardeniq.com/store/product/Rock-Dust,184,94.aspx