Agriculture Reference
In-Depth Information
Factors Affecting Soil Fertility
Soil Bacteria
Bacteria are tiny one-celled organisms that are found everywhere. In soil, a teaspoon of
productive soil generally contains between 100 million and 1 billion bacterial organisms.
They typically fall within one of the following functional groups:
• Decomposers
• Mutualists
• Pathogens
• Lithotrophs
The most common type of soil bacteria is the decomposer that consumes simple carbon
compounds, such as root fluids and fresh plant litter. Bacteria-based decomposing
processes convert energy from organic matter into forms useful to the rest of the soil food
web. Decomposers are especially important in immobilizing or retaining nutrients in their
cells, thus preventing a loss of nutrients. For example, decomposition keeps nitrogen in
a water-soluble form in the rooting zone rather than its normal gaseous form, which can
easily escape into the atmosphere. Mutualists form partnerships with plants - the most
well-known of them are nitrogen-fixing bacteria.
Bacterial pathogens can be harmful to plants. They include kinds like Erwinia , and certain
species of Agrobacterium . Lithotrophs or chemoautotrophs obtain their energy from
compounds of nitrogen, sulfur, iron, or hydrogen instead of carbon compounds. On the
other hand, some of these species are important to nitrogen cycling and the degradation of
One of the most well-known beneficial types of bacteria are nitrogen-fixing bacteria called
Rhizobia which are normally present in soils where legumes grow. Nitrogen from the air
is “fixed” or brought into the plant via a process where the bacteria infects the root hairs
Search WWH ::

Custom Search