How to
Rid Soil of Pests and
Diseases
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Soil-borne diseases can
spell disaster for plants.
In many cases, you can
control disease organisms by
mulching, rotating crops and
stocking the soil with large
helpings of organic matter.
But when you're dealing with
soil that's badly
infected--especially if
disease-bearing nematodes
are at work--you need to
wipe the slate clean.
Solarizing is the way to go.
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Steps: |
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1. |
Understand how solarizing
works: It raises the soil
temperature to around 150°F
(65°C), a lethal level for
garden culprits like fungi,
nematodes and Colorado
potato beetles. |
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2. |
To generate the necessary
heat, treat your soil in the
warmest, sunniest time of
the year--July and August in
most regions. |
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3. |
Dig or pull up all plants,
and till the soil to a depth
of 12 inches (30 cm). Remove
rocks, twigs and other
debris. |
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4. |
Rake the surface until it's
smooth, and shape it into
whatever rows, beds or hills
in which you intend to
plant. (You'll want to
disturb the soil as little
as possible after it's been
treated.) |
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5. |
Water until the soil feels
moist but not soggy, to a
depth of 2 feet (60 cm). If
you have very well drained
soil, lay a soaker hose
across the site (you may
need to provide additional
water during the treatment
period). |
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6. |
Cover the plot with a sheet
of 3- to 6-mil clear
plastic, and pile soil or
stones around the perimeter
to seal the edges. If you're
working with a raised bed,
make sure the plastic drapes
down over the sides. Leave
some slack in the cover so
it can puff up, rather than
burst or blow away, as the
heat intensifies.
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7. |
Install a second layer of
plastic if your climate is
cool, cloudy or humid.
First, place wooden blocks,
large stones or aluminum
cans every 4 to 6 feet (120
to 180 cm) across the first
cover. Lay down the second
sheet so that it floats on
top of the first, moving the
supports around if
necessary. Then seal the
edges with soil or stones.
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8. |
If you laid down a soaker
hose in step 5, pick up a
corner of the plastic after
a couple of weeks and feel
the soil. If it's dried out,
run the hose to replenish
moisture, then replace the
plastic. |
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9. |
In the Southwest, leave the
plastic in place for a total
of three to four weeks;
elsewhere wait six to nine
weeks. Then remove the
plastic; the soil is ready
for planting. |
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Overall Tips:
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If you don't want to put
your whole garden out of
action at the height of
summer, solarize one section
at time, beginning with the
most problem-ridden.
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If summer thunderstorms
occur frequently in your
area, try solarizing before
or after the height of the
stormy period; you'll stand
a better chance of clear
skies and intense sunlight.
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To boost the heat in cool
climates, before you cover
your plot, apply a 2-inch
(5-cm) layer of fresh manure
and mix it in well.
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Overall Warnings:
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Cultivate solarized ground
as little as possible. If
you till any deeper than 6
inches (15 cm), you'll bring
up untreated soil.
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