Agriculture Reference
In-Depth Information
larization efficacy. Organic matter additions and their subsequent decom-
position increases heat generation and increase the heat carrying capacity
of the soil
.
Volatile biotoxic compounds are released when organic matter
is heated during the process of solarization. Different plant residues or
manure incorporated into solarized soil may generate measurable amounts
of volatiles such as ammonia, methanethiol, dimethyl sulfide, allylisothio-
cyanate, phenylisothiocyanate and aldehyde. Thus, organic amendments
augment e biocidal activity of the soil solarization also. In addition, soil
treatment with organic and inorganic ammonia based fertilizers followed
by soil solarization may be effective against natural soil populations of the
damping off fungus (
Pythium ultimum)
,
Verticillium
spp., and root knot
nematode (
Meloidogyne incognita)
. Solarization appears to be an effective
practice able to control soil borne pathogens, even though it may cause
stress on some agriculturally beneficial soil microbial biomass. High so-
larization temperatures observed in high organic matter soils may kill the
microbiota of soil, including nitrifying microorganisms, and favor the ac-
cumulation of NH
4
-N. The lower rate of soil solarization temperatures ob-
served in low organic matter soils that allow the survival of soil microbiota
and promote aerobic conditions, with minimal liberation of nitrogenous
compounds, thereby resulted in nitrification and loss of N from the soil
(NO
3
is leached easily).
12.11 AGRICULTURALLY IMPORTANT AND BENEFICIAL
MICRO-BIOTA
Solarization raised soil temperature is considered mild compared to
steaming process in soil. Thus, soil solarization is more selective towards
thermophilic and thermotolerant biota, including actinobacteria (former
actinomycetes) which may survive and even flourish under soil solariza-
tion
.
Poor soil competitors such as many pathogens are killed by soil so-
larization since they tend to have specialized physiological requirements,
which are more adapted to coexistence with the host plants. This results
in a population shift favoring thermo-tolerant species such as fluorescent
Pseudomonads
and thermotolerant fungi. Solarization initially may reduce
populations of beneficial microorganisms, but populations of beneficial,
growth promoting and pathogen antagonistic bacteria and fungi quickly
recolonize solarized soil. Thus, soil solarization adds a biological control
