OrganicFarmer_AprMayFinal_e

STEPS FOR
SOLARIZING SOIL
are as follow
1
2
3
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Prepare soil for solarization.
For solarization to be effective,
tarps need to be as tight to the
soil surface as possible. All large
clods and rocks should be removed
from soil and soil should
be level. Solarization can be used
on raised beds or flat on soil. If
using raised beds, beds should
be shaped before solarization to
minimize soil disturbance after
solarization. Disturbing soil after
solarization can bring up untreated
seeds and pathogens from
lower in the soil to the surface.
Irrigate soil to field capacity to improve
heat transfer through soil.
Tarp can be applied by hand or
machine. If applying by hand dig
trenches around edge of application
area and bury tarps in
trenches. Cover with 2-3 inches
of soil. When applying tarp make
sure it is tight against soil surface
and held down all edges by soil.
Wait four to eight weeks then
take off tarp. Leaving tarp on soil
is not recommended as during
winter months tarp will act like
a greenhouse promoting weed
germination. Unfortunately, most
tarps are not recyclable so they
must be thrown in trash after
use. More durable tarps can be
reused if removed carefully.
For more information on soil solarization UC
ANR has some great resources at http://ipm.
ucanr.edu/PMG/PESTNOTES/pn74145.html
species (i.e., annual sowthistle) than
warm season annual species (i.e.,
redroot pigweed). Warm season species
common purslane can be challenging
to kill with solarization as it will
germinate in temperatures as high as
113°F. Other annual species which
require higher temperatures to kill
are those with hard seeds or thick
seed coats (Figure 2, see page 12, T.
Jacobs, unpublished data). Common
hard-seeded weeds are legume species,
bur clover and black medic, Malvacae
species, little mallow and velvetleaf, and
Erodium spp. (filaree). Perennial weeds
such as field bindweed and nutsedge
are difficult control with solarization
as well. For example, nutsedge tuber
mortality will not occur until exposed
to temperatures of 122°F or hotter
(Webster 2006). For control of perennial
and hard seeded weeds daily maximum
temperatures of 122°F or higher need
to be reached for at least a four-week
period (T. Jacobs, unpublished data).
Soil solarization can reduce the
disease incidence of many pathogens
to an economically manageable level.
Solarization will only provide control in
the first 8-12 inches
of soil. Therefore,
the control of some
pathogens, which
reside deeper in
soils, such as big vein
disease in lettuce is
limited (Iwamoto
and Aino 2008).
Additionally, mobile
soilborne organisms
can recolonize root
zones of plants after
solarization. This
makes control of
soilborne insects
such as garden
symphylans via
solarization difficult.
Before using soil
solarization, growers
should identify the
pathogens and other
pests in their soil
and consult experts
on whether soil
solarization is an
effective technique
for controlling the
soilborne organisms.
Solarization has
increased yields in
Bring the
heat on
hard-to-kill
weeds and
insects with
Distributed by
a variety of crops. Potential reasons
for increased yields due to solarization
are reductions in pathogen and
weed populations, larger availability
of heat solubilized nutrients such
as ammonia, and changes in plant
physiology (Candido et al. 2011). Costs
of solarization vary, depending on
plastic prices, but in general the plastic
costs are between $150-300 per acre
(Stapleton et al. 2008). Application costs
will depend on method of application
(machine or hand-applied). However,
due to yield increases and reduced
weeding time, solarization often pays
for itself and then some, particularly in
weedy or heavily diseased fields.
A wide variety of plastics are available
for use in soil solarization. The best
plastics are clear/transparent, 1-3
mils thick, and UV-inhibited to
prevent breakdown in sunlight. Most
agricultural plastic retailers have
solarization plastic available. For smaller
scale projects, thin (