Agriculture Reference
In-Depth Information
soil surface. Remove any large rocks, weeds or any other objects or debris
that will raise or puncture the plastic.
12.7
SOIL MOISTURE
Soil moisture is a critical variable in soil solarization because it makes mi-
croorganisms and weed seeds more sensitive to heat and also transfers heat
to living organisms in soil. The success of soil solarization depends on ad-
equate moisture for maximum heat transfer; maximization of heat in soil
increases with increasing soil moisture content. Soil moisture also favors
cellular activities and growth of soil-borne microorganisms and weed seed
germination, thereby making them more vulnerable to the lethal effects of
high soil temperatures associated with soil solarization. Wet soil conducts
heat better than dry soil to make soil organisms more vulnerable to heat.
Soil under the plastic sheets must be saturated to at least 70% field capac-
ity in the upper layers and moist to depths of 60 cm for soil solarization to
be most effective. The interaction between temperature and soil moisture
causes water cycling in soil during soil solarization. The upper soil layers
(upper 5 cm) have diurnal temperature fluctuations i.e., cooling at night
and heating to high temperature during sunlight hours. This diurnal fluc-
tuation causes moisture in the upper zones in soil to move downward as a
result of solar radiation during the daytime, while, at night the soil surface
cools and causes an upward migration of moisture. A drip irrigation sys-
tem line can be used under plastic mulch to maintain moisture in soil at
desired levels.
12.8
SOIL SOLARIZATION AND WEED CONTROL
Soil solarization frequently used for suppressing weeds growth and is con-
sidered a highly effective practice to control weeds. To solarize the soil,
first the soil must be in moist condition and covered with 0.125 mm thick
black polyethylene or 0.1 mm thick transparent polyethylene sheet for 4
to 6 weeks. The sheet should be in a full stretched condition and the edges
buried in the soil to hold the sheet in place. Due to solar radiation the soil
under plastic sheet gets heated up and the temperature inside the sheet
around 45-50°C. Due to heavy heat, weed seeds present in the soil under
the polyethylene cover gets affected. The effect of this soil solarization
