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In the book The Survival of Civilization, John Hamaker suggests
finely-ground glacial gravel because that is
nature's way throughout millennia to create
fertile soils. Glacial gravel, which is a
natural mixture of rocks, will create a broad
spectrum of minerals in the soil in a natural
balance.
Much of value can also be
gleaned from Europe and the research and
experiences there where single rock types and
combinations of single rock types such as basalt
are used.
Hamaker asserts that
"Micro-organisms select what they need to make
the compounds of life, and reject to the subsoil
what is not needed, [such as] aluminum, silicon,
iron, etc., which are generally in excess [in
gravel dust]," further pointing to "the Kervran
research on biological transmutations", which
suggests that biological organisms may play an
active role not only in selecting specific
elements, but also in modulating their elemental
nature to create needed materials where they are
in short supply. Hamaker says "As long as the
soil is neutral [in pH] or close to it,
microorganisms will control what goes into the
plant roots. These controls are off when the
soil is acid or acidic chemicals are added."
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Composting with rock
dust
Combining gravel dust with
organic materials in compost is a great way to
solve application problems and speed up the
process. Don't forget a handful of soil to
inoculate with organisms. Gravel dust improves
aeration and structure and therefore prevents
rotting. Gravel dust is assimilated even more
quickly in compost than in poor soils.
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Compost and gravel dust
are a symbiotic combination: the compost
provides an excellent medium for the
"microorganism population explosion" promoted by
the dust, and the gravel dust will not only help
create more organic matter, but will also help
hold it in place, reduce odors and conserve it.
Add 2-20 lb. of rock dust
per cubic yard of compost, if one is doing pile
or window composting.
Soil acidity
Soil pH should be measured
annually. If the soil is acidic, agricultural
limestone may be added together with the rock
dust to bring the soil pH to neutral. Gravel
dust will also neutralize soils to a great
degree, but limestone is a quick remedy for
agricultural soils. Limestone is not recommended
for forests as it will destroy the
humus-building complex in the long term.
Keep insects in
natural balance in your garden
For short-term rescue,
very fine dust sprayed directly on plants and
trees has been shown in research in Germany to
deter insect infestations very effectively.
Trails of rock dust around the garden help keep
slugs out. And healthy remineralized plants will
not be plagued by insect infestations in the
future as they become healthier and more insect
resistant.
How to apply gravel
dust
There are many ways to
apply dust to the soil; which method you use
depends on the scale and your preference. It can
be spread by hand out of a wheelbarrow using a
shovel, or roto-tilled and disked in. You can
use a wet agricultural lime spreader. If
equipment is available that contains an agitator
(to maintain particles in a suspended state), a
wet spray can be used.
Organic farmer John
Sundquist in Oregon applies it with a manure
spreader, bander or an "E-Z Flow" type
fertilizer applicator. He also uses rock dust in
a potting soil made of compost, ashes and peat
moss.
How much to use
A grower of crops or a
gardener needs a good response the first year
after a fall application. The response in any
one year depends on the amount of minerals
available to the microorganisms, soil moisture
and the amount of inert organic matter.
If the last two factors
are satisfactory, as little as 3 tons of gravel
dust per acre worked into the top 4 inches of
soil should give good results. However, I prefer
about 10 tons per acre worked in about 8 inches,
since one application will eliminate the cost of
a number of more frequent applications and give
high yields.
The
Application Conversion Chart
will help you
to determine how much gravel dust to use: 3
tons/acre is considered the minimum application,
10 tons/acre is Hamaker's preferred long-term
application, and 20 tons/acre is given as a
major remedial application for especially dry,
poor soil. Smaller amounts are recommended if
the rock dust is finer than 200 mesh and larger
amounts if much less fine than 200 mesh.
Finding local
sources of gravel dust
To find gravel-grinding
operations in your area, call your local gravel
pit (look in the Yellow Pages under
"Cement-Wholesale", or "Sand and Gravel") and
ask if they have crushed gravel screenings made
from mixed rocks, the kind that comes out of
river beds - crushed and passed through a 1/4
inch or finer screen. The gravel dust will
probably cost from $1-$8.00 per ton plus the
cost of transportation if the gravel pit
delivers it to your garden. As most of the cost
is in transporting the rock dust, having a truck
or access to one is an advantage. A cooperative
initiative with friends and neighbors would also
cut costs down.
The
Particle Conversion Chart
shows various
categories of "soil separates" (ground
particles) listed with their diameters in
microns (thousandths of a mm.) and their
corresponding screen mesh sizes. "Mesh" simply
refers to a screen with a given number of holes
per inch.
The more finely ground the
rock, the more readily microorganisms will have
access to the minerals. John Hamaker uses the
term "gravel dust" to mean a dust "90% of which
will pass through a 200-mesh screen."
You can also contact your
local state Aggregate Producers Association,
your local county DPW (Department of Public
Works), your state DOT (Department of
Transportation) Materials Bureau and you can
contact the National Aggregate Association (Tel:
1-800-622-1020).
What does industry
call the product?
It is referred to as pond
settlings, rock dust, rock flour, classifier
tailings, and minus #200 mesh. You should ask
for minus #200 Mesh (-75 micron) material, pond
settling, material that has gone over the weirs
of a sand screw or the weir of a sand
classification tank, or material obtained from
the dust collection system. You should not use
concrete sand, abrasive sand, filter sand, mason
sand, blow sand (loess) screenings as they are
too coarse.
What is the best
material to use?
Glacial sand and gravel
that contain a myriad or heterogeneous
combination of various rock formation type or
mineralogy is preferred.
Other metamorphic or
igneous stone such as basalt, rhyolites, etc.,
are highly recommended. Most sedimentary rocks
(limestone and dolomite) are used to balance pH
and provide for calcium and magnesium
deficiencies.
Testing your gravel
dust
Several people have
reported that gravel dust does not work or it
will have [only] a temporary effect. They don't
describe the dust in detail, but there may be
very little dust in what they call 'dust.' Know
what you are buying or you may be badly
disappointed.
Here are three simple,
quick tests you can perform at home:
POT TEST: A pot
test will give you immediate, practical proof of
what the product will do in the soil. It is a
good idea to add the gravel dust to clay pots
and plant radishes or other fast growing plants
and observe their progress. As John Hamaker
writes: "Doing a pot test is the most convincing
argument I know of. Anybody can do it. There are
testing laboratory grinders everywhere. There is
no lag time. In 6 hours you can get a
microorganism population explosion. Taking some
6" clay pots, I filled them with a 50-50 mixture
of earth and peat and 3 heaped tablespoons of
dust. The results were astonishing!"
You can compare different
mixtures or samples of gravel dust depending on
what's available in your area. Use a control
without rock dust to compare as well. You can
also begin with small plots in the garden. You
can see the results of the gravel dust you've
chosen and then add it in larger quantities to
your garden. Work the gravel dust into the
topsoil, if possible.
SEPARATE LAYER TEST:
Purchasing a product based on its stated screen
mesh alone still leaves room for error. A
purchase of 90%, or even 100%, of minus #200
mesh screenings could contain only sand and
silt, and no true dust. This test will tell you
approximately how much of your "dust" is really
dust and will be suspended in water.
Fill a clear glass half
full with your sample and cover it with about
two inches of water. Shake it up vigorously,
then allow it to settle overnight. The dust,
silt and sand will settle into three distinct
layers with the dust at the top.
If the container is
allowed to stand until the water has dried out,
the dust [topmost] layer will shrink to about
1/3 the original measurement and give a more
accurate percentage of the dust. Your first
observation, however, will tell you if you are
buying mostly sand. The coarser the grind, the
less effective it will be in the soil, and the
more you will need to use per acre.
MOISTURE TEST: If
the material is bought by the yard, there is a
probable increase in bulk when wet. The buyer
needs to test so one can know the actual weight
of dust one is applying to the land. Take a
sample, weigh it, then dry it thoroughly in the
oven [and re-weigh it]. This will tell you how
much of the weight you are buying is moisture.
Chemical analysis
In some, but not all,
situations, having a formal chemical analysis
may not be necessary. A pot test and small-scale
trials with fast-growing plants will give you
more accurate information and with less expense.
In cases where you have doubt about its source,
you may wish to have a gravel dust analyzed to
ensure that it is free of radioactive elements
and toxic industrial by-products. In most cases
your source will have already had to undergo
such testing in order to get a license to
operate. This is worth some homework. If you are
not able to obtain documentation to your
satisfaction, it might be wise to go ahead and
obtain your own independent lab tests. Good
testing labs are listed in Sources and
Resources.
More tips from
Hamaker
"One other thing might be
useful. I put about 2 inches of sand on our
garden before plowing. It will last a long time
and give some yield after the dust is used up. I
am sure it has been contributing to what we
grow. Unscreened sand (preferably fine sand)
from a local gravel pit is much more economical
than shipping dust which is mostly silt and fine
sand.
Sometimes the gravel pits
have mesh screens and can measure the exact
fineness of the gravel. Though it may be hard to
find the ideal fineness - 90% passing through a
minus #200-mesh screen - it may be practical to
use even if only 20% or so passes through a
minus #200-mesh screen and at least 50% passes
through a #100-mesh screen. You will have the
finer material immediately available to the soil
and the rest will break down over time. If most
of it passes through a minus #200-mesh screen,
it will have a fine consistency like flour or
cement. The gravel pit may have machinery to
crush the rock finer and may crush it for you."
Soil erosion is an effect
of the shortage of minerals available to support
the soil organisms. As Hamaker says, "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."
For a more thorough
understanding of SR, read The Survival of
Civilization
and order the Research Packets
available through RE, Inc.
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