Agriculture Reference
In-Depth Information
rate of SOM. Usually the leguminous family is used as green fertilization,
because they are high in N, produce high amounts of fresh tissues quickly and
can easily grow under almost all kinds of soil conditions. Accordingly,
legumes are used in different rotation to enhance soil conditions for plant
growth and microbial activities (Albiach et al., 2000; 2001).
Compost is the product of different municipalities' wastes, produced by
microbial activities. Production of compost is very recommendable as it can
recycle different wastes, which are not favorable to the environment and
human health, to some very useful products for the environment and crop
production. However, different compost properties such as salinity and the
presence of heavy metals must be tested before compost can be used for crop
production (Wong et al., 1999).
Vermicompost is also similarly produced; however, earth worms are also
applied to the compost. Through feeding on compost, earth worms are able to
produce vermicompost, which is high in organic matter, nutrients and
microbial activities. during the process of vermicomposting earth worms can
turn organic matter into some smaller pieces, by the production of different
enzymes in their gut and produce more useable organic matter for the use of
soil microbes (Atiyeh et al., 2000). Sewage sludge is also a source of organic
matter; however their properties must be tested before use, as usually they
have a high rate of heavy metals, which are not favorable to crop growth and
the environment (Tsadilas and Dimoyiannis, 1995).
T
OP
S
OIL AND
S
OIL
M
ICROBES
Top soil is the most fertile and hence the most biologically active layer of
soil. It is because the highest rate of SOM is accumulated in top soil.
Accordingly, the highest microbial population and diversity is located in top
soil. There is a wide range of microbes found in top soil with different
activities. Soil microbes are able to mineralize SOM, immobilize and oxidize
nutrients, mineralize (amonify and nitrify) organic N, denitrify mineral N, fix
nutrients and may also have pathogenic effects on plant growth (Doran et al.,
1998). Recycling nutrients in ecosystem is one of the most important functions
of soil microbes. Through the above mentioned processes, soil nutrients
become either mineralized or immobilized by soil microbes. Mineral nutrients
present in the structure of organic compounds become available for the use of
plants and microbes by the process of microbial mineralization (Miransari and
Mackenzie, 2010, 2011a,b).
