Types of Deep Soil Preparation
GROW BIOINTENSIVE bed until good structure is
established. Afterwards, one will depend on surface
cultivating the top 2 to 4 inches. Another way to keep
cultivating the top 2 to 4 inches. Another way to keep
soil loose between double-digging is to single-dig
(loosening the top 12 inches with the spading fork). We
recommend doing so between crops in the same growing
year.
General Double-Digging Procedure—Each year
before the main crop until good soil structure is
established
Spread a layer of compost over the entire area to be dug.
After marking the bed, place the digging board on the
bed, leaving approximately 24 inches from the end of
the bed for the +rst trench. Remove 7 +ve-gallon buckets
of soil from the upper level of the +rst trench (assuming
a 5-foot-wide growing bed; see illustration on this page).
Be sure to dig trenches across the width of the bed. This
will give you 3 buckets of soil to make compost (these
will eventually be returned to the growing beds in the
form of cured compost), 1 bucket of soil to make flat soil
to grow seedlings, and the remaining 3 buckets are
returned to the bed after it is dug.
The Initial Double-Dig Process: Step-by-Step
1. Spread a layer of compost over the entire area to be dug. (Compost is added after
the double dig and bed shaping for Basic Ongoing Double Digs
width of the bed and put the soil into buckets or a wheelbarrow for use in making
compost and flat soil. If the bed is 5 feet wide, the soil will fill 7 five-gallon buckets.
(The trench is being dug across the width of the bed.)
to its full depth and then pushing the tool handle downward so the fork tines will
lever through the soil, loosening and aerating it. (See following illustrations for
loosening compacted soil.)
3b(i). FOR COMPACTED SOIL: While standing in the trench, loosen the soil an
additional 12 inches with a spading fork by digging in the tool to its full depth and
lifting out a tight soil section on the fork pan.
3b(ii). Then, by moving your arms upward in a small jerk, the soil will break apart as it
falls downward, hits the fork tines, and falls into the hole below.
Now, standing in the trench or on the digging board
above the trench, dig down another 12 inches (or as
deep as possible) with a spading fork, a few inches at a
time if the soil is heavy or tight. Leave the fork as deep
as it has penetrated, and loosen the subsoil by pushing
the fork handle down and levering the tines through the
soil. If the soil is not loose enough for this process, lift
the chunk of soil out of the trench on the fork tines.
Then throw it slightly and gently upward, and allow it to
fall back on the tines so it will break apart some. If this
does not work, use the points of the fork tines to break
the soil apart. Work from one end of the trench to the
other in this manner.
Next, move back the digging board (approximately the
12-inch width of the next trench). Dig another trench
behind the +rst one, moving each spadeful of the top 12
inches of soil forward into the +rst trench. When digging,
make as few motions and use as little muscle as possible
in this process. This will conserve your energy and
involve less work. In fact, as you dig the soil, you will
discover you can use an Aikido-like economy of motion
and energy in which you are virtually just shifting your
balance and weight rather than digging. Sometimes you
will have to work over a trench a second or third time to
remove all the soil and obtain the proper trench size.
Repeat the subsoil loosening process in the second
trench.
spadeful of soil forward (into the first trench), mixing the soil layers as little as
possible.
Dig a third trench, and so on, until the entire bed has
been double-dug. It helps to level the soil with a rake
every 3 to 4 trenches during the digging process. If you
do not, you may end up with a very deep trench at the
end of the bed. Then you will have to move a large
amount of soil from one end of the bed to the other to
amount of soil from one end of the bed to the other to
even it out when you are ready to be +nished. This
action also causes a disproportionate misplacing of
topsoil into the subsoil area.
When you are sliding the soil forward from one trench
into another, notice a couple of things. If you spread
compost on the bed before beginning, note that some of
the layer slides 3 to 6 inches down into the trench,
creating a small mound of soil or landslide. This
approximates the way nature adds leaves, &ower bodies,
and other decaying vegetation to the top of the soil,
where they break down and their essences percolate in
the soil.
Always make sure that the upper layer of soil (the top
12 inches) is not turned over during the double-dig. Most
of the microbiotic life lives in the upper 6 inches of the
soil. Also, the natural layering of the soil that is caused
by rainfall and leaching, leaf litter, temperature, gravi0ty,
and other natural forces is less disturbed when the soil is
not generally mixed, even though the soil is loosened up
and distributed somewhat. Aim for a balance between
nature’s natural strati+cation and the loosened
landsliding soil. (As a goal, strive not to mix the soil
layers. Even though some mixing will occur, it is
important to avoid excessive disruption of the soil
layers.)
When you are through double-digging, the aerated
surplus soil in the bed will be enough to +ll the +nal
trench at the end of the bed. You may also add some of
trench at the end of the bed. You may also add some of
the buckets from the +rst trench. If you add compost that
you have made with soil, that will also contribute soil to
the bed.
Take buckets of surplus soil to the soil bin pile.
Level and shape the bed. Sprinkle on compost and any
soil amendments as recommended by your soil test over
the surface of the bed. These may include organic
nitrogen, phosphorus, potash, calcium and trace mineral
fertilizers. (For more detail, see this page.) Include any
pH modi+ers (such as special leaf or pine needle
compost to make the soil less alkaline, or lime to make
the soil less acid) as indicated by your soil test. Sift in
compost and fertilizers and pH modi+ers only 2 to 4
inches deep with a spading fork. After sifting them in, do
no further raking to avoid disturbing the even
distribution of fertilizers and compost.
Considerations for Initial Dig with Very Poor Soils
You may choose to add compost at di)erent points for
the initial double-dig and when working with a soil with
very low amounts of organic matter. Instead of applying
compost only after the double-dig, consider spreading a
½-inch layer over the bed before double-digging and/or
a ½-inch layer during the dig by incorporating it
thoroughly into the 12-inch-deep trench.
