Agriculture Reference
In-Depth Information
Vay, 1982). After solarization has completed, the clear polyethylene mulch
can also be used as bed mulch. The thin polyethylene mulch can have the
tendency to rip in certain spots. If the mulch rips, it will let out moisture
and heat, which are necessary to the success of solarization. Sealing the
rip with plastic tape will easily remedy any rips that occur as reported by
(Sayed and Malakar, 2004). The overwhelming amount of advantages over
the minimal disadvantages makes soil solarization an attractive choice for
organic farmers that live in temperate climates.
12.3
PRINCIPLES OF SOIL SOLARIZATION
• Utilization of transparent polyethylene because of transmission of
most of the solar radiations directly to the soil. As black polyeth-
ylene sheets absorb heat and do not conduct heat downward. The
thinnest polyethylene film of 25-μ size is the most effective and eco-
nomical to use. Polyethylene films contain additives that improve
their properties for use in solarization. Additives include pigments,
heat-retaining substances, ultraviolet stabilizers and biodegradable
additives (Stevens et al., 1991). Chase et al. (1999) and Campiglia
et al. (2000) observed that soil temperatures under transparent film
were higher than under black mulch, while Ham et al. (1993) report-
ed the opposite. Rieger et al. (2001) found black and clear mulches
equally effective for increasing soil temperatures.
• Solarization should ideally be done during the summer months, when
high air temperatures and intense solar radiations are available.
• Soil should be kept moist to increase thermal sensitivity of fungal
'resting' structures such as sclerotia, chalamydospores, etc. and to
improve heat conduction. A single deep irrigation prior to treatment
is likely sufficient, but additional moisture may enhance solarization
process. Drip irrigation technology may be used under the film for
additional water.
• Longer solarization periods will greatly improve pest organism con-
trol particularly at greater depths because physical, chemical, and
biological control interactions may be involved and a variety of pests
are controlled.
• A single clear plastic layer laid on the soil surface can greatly increase
solar soil heating and provide good control of weeds and pathogens.
