Agriculture Reference
In-Depth Information
Higher organic matter in soil, as a result of higher growth of plants and
higher microbial presence can decrease the amounts of CO
2
in atmosphere and
hence control the greenhouse effect and the atmospheric climate. In other
words, higher crop and forest production can control the rate of global
warming by decreasing atmospheric CO
2
(Six et al., 2004). Hence, C fixation
by plants as resulted by photosynthesis process can both produce food and
affect the atmospheric climate. Plants can also influence the climate through
absorbing sun energy and the process of evapotranspiration.
There are different parameters affecting the quality of SOM including,
climate (Hartley and Ineson, 2008) soil and plant type, soil tillage (Riley et al.,
2008) and soil microbes. Plants adopt themselves with climate. Under humid
and temperate climate, plant tissues are more fresh (higher water availability)
and are mineralized more easily as the conditions for microbial activities are
more favorite. However, in arid or semi arid climate, there are much less water
available for plant use and plant tissues become more woody to decrease water
transpiration and preserve more water. Accordingly, such tissues are
decomposed at a lower rate as their biochemical structure is more resistant to
microbial mineralization and because the conditions are not very favorable for
microbial activities (Jensen et al., 2005).
The effect of soil tillage on SOM is through affecting SOM mineralization
rate, soil temperature and soil structure. Soil tillage results in higher oxygen
flux into the soil and hence higher SOM mineralization by soil microbes. In
addition improved soil structure by soil tillage may also enhance soil microbial
activities resulting in the increased rate of SOM mineralization. Hence, soil
tillage increases the rate of SOM reduction in soil. Furthermore, no- or
reduced tillage increases C sequestration in soil (Galvez et al., 2001). The rate
of C accumulation by cereals is higher than legumes, because legumes tissues
are decomposed more rapidly than cereals tissues. Similarly in a rice
monoculture more organic matter is built up in soil relative to a rice-wheat
rotation, because in the latter case soil is aerobic in a part of growing season
resulting in the mineralization of soil organic matter (Aggarwal et al., 2000;
Dawe et al., 2000).
With respect to the significant effects of organic matter on soil properties,
it is favorable that SOM is restored regularly. There are different methods by
which organic matter can be applied to the soil. Use of manure, green
fertilization, compost, and vermicompost and sweage sludge is among the
most common ways to restore SOM. The origin of manure determines its
properties as manures with different origin or sources differ in their rate of
available nutrients. Green fertilization is also a useful method to increase the
