Agriculture Reference
In-Depth Information
capacity and soil water holding capacity (Riley et al., 2008; Hartley and
Ineson, 2008).
Soil microbes are among the most important components of each
ecosystem enhancing soil efficiency. It is because soil microbe are able to
perform some very important functions affecting soil and hence ecosystem
properties. Soil microbes are able to recycle nutrients in organic matter
resources and make them available for the use of plants and soil microbes. In
other words SOM is mineralized by some specific soil microbes and as a result
carbon dioxide (CO
2
) is emitted and nutrients become available. This would
also improve soil structure and other properties by adding humus to the soil
(Tu et al., 2006; Widmer et al., 2006).
There are different types of microbes in soil including beneficial and non-
beneficial ones. The beneficial soil microbes include arbuscular mycorrhizal
(AM) fungi, N-fixing
rhizobium
and plant growth promoting rhizobacteria
(PGPR). The non-beneficial soil microbes include plant pathogens in soil
(Badri and Vivanco, 2009). AM fungi have some profound effects on
ecosystem components affecting yield production and environmental health.
AM fungi can increase water and nutrient uptake by their host plant, improve
soil structure, alleviate soil stresses, control pathogens, and affect other soil
microbes (Miransari, 2010a, b). Soil fixing bacteria,
rhizobium
can fix
nitrogen (N) by developing a symbiotic association with their specific host
plant (Miransari and Smith, 2007; 2008; 2009). PGPR are soil microbes
enhancing the availability of different nutrients to the plants and microbes
usually non-symbiotically. All these microbes are mostly found in the top soil
and hence can significantly contribute to soil productivity.
Processes such as erosion, which causes the removal of top soil by water
or wind, are not favorable to the soil properties, adversely affecting plant
growth and microbial activities. As a result of soil erosion the top soil layer is
moved away, and hence the most valuable part of the soil, which supplies
nutrients to plant growth and yield production, is reduced. Since a long time is
necessary for the production of top soil attempts are continuously made to
decrease or control the process of erosion. Soil organic matter, structure, cover
plant, controlling water flow and addition of organic fertilization are among
the most influencing parameters on the process of soil erosion (Evans et al.,
2005; 2006). As a result of soil erosion soil particles move into different water
resources, decreasing their storing capacity. This is why the alluvial horizons
(leached soil horizons, which are deposited in new places such as a river bank
or delta) are very fertile.
