Soil food web series: Bacteria, the little nitrogen factory

Ok, enough about human anatomy, back to the soil. Bacteria in the soil are not as mobile as fungi; they attach themselves to the plant root or live near the plant root. The component of soil carbon known as active carbon is the most nutritious and preferred by this group of microorganisms. The life cycle of a single bacterium in soil is short-lived, as bacteria mostly serve as a food source for other soil microbes such as protozoa and some nematodes. Its death in the soil through this process is however not in vain as it contributes to the mineralisation of nutrients in the soil. When bacteria are fed on by other organisms, its population is kept at a balance. If there are no organisms to control the population growth, then there is a high chance of nitrogen deficiency developing in that soil. This is because bacteria have a high requirement of nitrogen when decomposing organic matter. This high requirement competes with the plants requirement for nitrogen, resulting in a deficiency. Nitrogen fertiliser is usually applied near or in the root zone, where bacteria is most abundant, and it is expected that some of the nitrogen fertiliser will end up being consumed by soil bacteria. If bacterial growth is uncontrolled in soil, then the plants will suffer from nitrogen deficiency even though nitrogen is being applied thoroughly.

The soil will never run out of bacteria, what is of importance is to make sure that there are enough organisms to control their multiplication so as to benefit effectively from their presence.