Re: CULT: colors/thickness plastic films solarization
- Subject: Re: CULT: colors/thickness plastic films solarization
- From: L* M*
- Date: Sat, 29 Jun 2002 18:20:29 -0400
Rummaging around on the web using Google turned up a lot of experimental
stuff on solarization/mulches & colors/thicknesses of various plastics:
<An assumed air gap of 0.65-mm [between soil surface and the plastic
film] provided greater soil heating by black than clear films. For
larger air gaps this order of heating is reversed.>
<Color affects the surface temperature of the mulch and the underlying
soil temperature. Black is the most commonly used color of polyethylene
mulch. Soil temperatures under black plastic mulch during the daytime
are generally 5°F higher at a 2 inch depth and 3°F higher at a 4 inch
depth compared to that of bare soil. Daytime soil temperatures under
clear plastic mulch during the daytime are generally 8° to 14°F higher
at a 2 inch depth and 6° to 9°F higher at a 4 inch depth compared to
that of bare soil. However, the use of clear plastic mulch requires the
use of a herbicide or fumigant to control weeds.>
<[solarization]5. Use clear polyethylene, not black mulch. Sunlight
passes through clear plastic to heat the soil directly. Black plastic
intercepts the sunlight, and soil
is heated by conduction where soil contacts the plastic. Some of the
heat generated when sunlight hits black plastic is lost directly to the
outside air. Clear plastic produces significantly higher soil
temperatures faster than black plastic.
6. Thin plastic mulch (1 to 2 mil) may permit more sunlight to penetrate
to the soil and has been reported to favor more rapid and deeper
control of soil-borne fungi than thicker plastic (6 mil). However, equal
control was eventually obtained with both thicknesses.>
<The process [of solarization] is carried out in summer and works best
in regions that have hot, sunny weather for 4 to 8 weeks straight;
daytime temperatures above 80 degrees F/27 degrees C are ideal.
Solarization isn't very effective in coastal climates with summer fog,
nor does it work well in very windy areas. Soak soil to a depth of 1
foot: moist soil conducts heat better than dry soil and initiates
germination of weed seeds, which will then be killed by heat.>
<3. Cover soil with 1- to 4-mil clear plastic; use UV-resistant plastic
if it's available, since it won't break down during solarization.
Stretch plastic tightly so that it is in contact with the soil. Bury the
edges in the perimeter ditch. An optional second layer of plastic
increases heat and makes solarization more effective; use soda cans as
spacers between the two sheets
Leave plastic in place for 4 to 6 weeks (8 weeks for really persistent
weeds); then remove it. (Don't leave it down longer than 8 weeks, or
soil structure may suffer.) You can now plant. After planting, avoid
cultivating more than the upper 2 inches of
soil, since weed seeds at deeper levels may still be viable.>
Linda Mann east Tennessee USA zone 7/8
American Iris Society web site <http://www.irises.org>
iris-talk/Mallorn archives: <http://www.hort.net/lists/iris-talk/>
iris-photos/Mallorn archives: <http://www.hort.net/lists/iris-photos/>
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