[permaculture] [Fwd: More thoughts on double digging while preparing raised garden beds. (revised post)]

Lawrence F. London, Jr. venaurafarm at bellsouth.net
Tue Dec 22 01:38:57 EST 2009

I'll probably add to this very post continuously. Anyone interested 
please append your input anywhere you see fit in the text. This could be 
posted to the Wiki eventually when it is complete enough. Just this time 
I will add material from my garden hand tool sourcelist on soil quality
-------- Original Message --------
June 08, 2008

"Emilia Hazelip (1938 - February 1, 2003) was an organic Permaculture
gardener who was born in Spain and began gardening seriously in the late
'60s. A former Merry Prankster and pioneer of the concept of synergistic
gardening, her farming methods were inspired by the work of Masanobu

Where Fukuoka focused most of his attention on orchards and the
rice/barley crop rotation, Emilia Hazelip focused on creating and
maintaining market gardens of vegetables and herbs.

Emilia Hazelip, who introduced the concept of permaculture to France
over a decade ago, drew on many sources as she continued to develop
gardens. The work of Permaculturist Marc Bonfils with self-fertile
cereal production and the microbiological research of Alan Smith and
Elaine Ingham are frequently mentioned.

To see more videos by the maker of this film and for contact information
on how to purchase a high quality full length version (SVHS) on DVD
please visit: http://www.youtube.com/user/BULLEBOULO

For More Information on the Global Permaculture Movement Please Visit:


That is the way to build a raised bed though there are important details
(the ones the devil is in) that need to be considered, many based on
soil type, access to water, climate and lay of the land.
She is exactly right about the dimensions of the bed in the design she
recommends except that one needs the ditch (a very narrow path) between
the beds _to extend below grade 25% to 40% of the total bed height_ thus
extending the actual working height of the beds considerably. You
provide extra aeration for the part of the bed below grade that is
exposed to the ditch between the beds. The other dimensions she suggests
are perfect, 4 feet wide (measured approximately
across the bed exactly at existing grade level. This bed width can be
modified according to the height of the gardener(s) so that they will be
able to do any work needed, leaning over to reach the middle, but not
having to put their foot on the bed to keep from falling forward, which
would induce compaction in those places (and that is a real issue with
your prized, hard-won, mature, permanent beds). The 20 inches between
beds (measured at existing grade as shown in the diagram) is ideal. Of
course you put all weeds removed from the garden into this ditch to
conserve water, create a walking path protecting the soil underneath
from compaction and as they decompose they provide beneficial
microorganisms and nutrients (compost tea) to leach into the garden soil
for added tilth and fertility, food for soil dwelling creatures and
particulate matter for them to use in constructing their habitat; soil
colloid and soil crumb structure are keywords in this instance.

What a fallow biointensive permanent notill raised bed looks like after 
a few years is a solid porous mouldy living organism hosting resident 
critters of all types. It just has a certain look to it, kind of like an 
organic fire ant mound built by micro permaculturists heavy into compost 
use sharing their bunker with earthworms and fungi. It is a structure 
that you only want to disturb when you need to remove weeds from the 
top, create a shallow loose seedbed or plant seedlings directly in it.

Double Dug Biointensive Garden Preparation

The essence of it is that you invest a lot of effort and materials up
front, inverting the soil, fragmenting the crumb structure, with
associated temporary disruption of soil life and soil structure,
oxidation of organic matter and release of co2 through exposure of humus
to air in order to improve soil tilth, fertility, drainage, water 
holding capacity,
cation exchange capacity, organic matter content and overall soil 
quality provifing an
improved and healthy medium for hosting beneficial microorganisms and 
other creatures
that make garden soil their home. You remove much of the soil in the 
bed, add organic
matter and mineral based soil amendments to it, homogenize these 
materials then
return the amended, enriched soil mix to the bed. This is done in
increments of one (typical short (42" to 48") English D-handled *see 
below) digging
spade blade width wide and one spade blade length deep for the width of
the bed (38-50" wide depending on the gardener's height).

You want highly mineralized soil, high in tilth and fertility, producing 
vegetables and fruits with exceptional flavor.
Add rock dust from quarries to your garden soil for trace minerals, 
microbe food and tilth, permanently eliminating soil
compaction. This is called siltation pond fines. It is so fine that if 
you put some in a glass of water it turns cloudy
and stays that way for quite a while before settling into a layer of 
sludge on the bottom; so fine it would take a microscope
to see the individual particles. This is great material to feed plants 
and soil microorganisms and invertebrates in your garden.
I think we are talking 200 mesh or finer; some fines are a little coarse 
by comparison to my basalt/tuff fines and some are an
aggregate with the largest component almost microscopic, like the talcum 
powder in pyrophylite fines (dredged from the quarry's siltation ponds).
To prevent compaction, permanently, fines act mechanically to interfere 
with clay and silt particles that when compressed when wet become highly
compacted when dried out - a serious problem for gardeners needing 
productive high-tilth soil.
I have used  this material to enrich soil for the benefit of plants, 
microorganisms and invertebrates and to permanently
prevent any compaction of my soil that would significantly reduce the 
productivity of the gardens. The materials include
"siltation pond fines" from the following types of rock: granite, 
volcanic tuff (maybe basalt, very hard rock, 2nd hardest in NC)
and pyrophyllite screenings. I am glad to hear that granite, high in 
silica is a sink for lime making my soil acidic,
good for most crops, pH 6.1 to 6.6 or so. Tillage is expensive, 
disruptive of soil life and inconvenient when it needs to be done
and the soil is too wet; i.e. weeds can get out of control and go to 
seed when tillage can't be done, like in Spring, to remove them and
create a fine, weed free seedbed for new plantings. Fines are mixed with 
existing soil on site, sometimes in a 30 or 40 to 50 ratio.
The clay or silt particles become permanently separated from each other 
and cannot be seriously compacted again.
This effect is also achieved with the addition of compost or manures to 
the soil. The fines feed the microorganisms
that help break down the fines and make trace minerals available to 
plants; these microbes also break down any raw or composted organic matter
added to soil to become humus, feed released nutrients to crops and 
improve the soil crumb structure providing added tilth to your garden soil.
The extra trace minerals in garden soil makes crops taste much better. 
The famous tomatoes grown in volcanic soils in places in Italy taste so
good for this same reason. That's how fines reelieve compaction and add 
to soil health and vitality, crop health and disease and predator
resistance and crop flavor, appearance and keeping qualities. More about 
fines dissolved in water. In places in the high country areas in
Eastern countries people drink cold river water that is cloudy and high 
in mineral content; they live long lives.

I would remove the top 8" or more of your raised bed-to-be. Then, "in 
situ" (without turning or inverting the soil layers) tilth
or dig up and pulverize an additional, lower 8-12" of subsoil; add 
amendments of all sorts to the 8" of soil you removed then put
it back in place on top of the subsoil layers you just tilthed - then 
you will have a "raised bed", the new garden bed surface will
now extend 4-8" above existing grade.

This will address any concern about your garden drying out during 
drought times if you use raised beds. The benefits outweight the
disadvantages aand with the following technique you will have no 
problems whatsoever.

Avoid having paths between the beds that are level with existing grade 
but ditches or furrows between the beds. These provide
much needed drainage and you can fill these ditches with mulch, weeds, 
hay, etc all the way up to the tops of your raised beds.

You want to to accomplish the objective of increasing depth of tilth and 
fertility in the soil in your beds. Mulching the top layer is
mandatory. Mulch will decompose leaving the seedbed fine and loose while 
leaching humus and compost tea into lower layers of garden soil
including sub soil areas to depths of several feet (partly because you 
have already tilled this zone). You want a permanent, notill,
biointensive raised bed that gets better each year through the action of 
compost tea, humus and nutrients that leach from the top layers
into the lower layers; that's a real "trickle-down bioeco-economy" with 
big pay back in quality produce for the table and for market.
This is real Pay Dirt as J.I. Rodale described it.

After this process is completed you need never again turn your soil,
except to a depth no greater than is necessary to control newly emerging
weeds, break crust and create a fine, loose seedbed. You now have
biointensive no-till, permanent raised beds.

This technology has been around for centuries and it works.
There is a very big net gain for soil, its inhabitants and the environment.

See John Jeavons books, Alan Chadwick's literature and lectures (links
on my website) and Aquatias' "Intensive Culture of Vegetables, French

Double  digging is as essential and indispensible to gardening anywhere
in the world, where the climate does not mandate other methods, as grain
is to bread.

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