Roles of Microorganisms in Organic Matter Transformation
Conversion of ammonium to nitrate (NO–3) nitrogen. Ammonium is first converted to nitrite as in the equation: above with the activity of Nitrosomonas bacteria, a group of obligate autotrophs which have as their sources of energy the oxidation of simple molecular substances such as NH4+, Nitrite (NO2) is then rapidly converted to nitrate (NO–3) through further oxidation by another group of obligate autotrophs.
In well-aerated soils, step (ii) above follows step (i) very quickly that there is no accumulation of nitrite which, if otherwise, could be injurious to plant roots.
In cases where a large amount of ammonium fertilizer has been applied to alkaline soil, the conversion of nitrite to nitrate is delayed until after the ammonium ion concentration has reached a relatively low level.
It should be noted that plants take up nitrogen in both the ammonium (NH4+) and nitrate (NO–3) forms from the soil solution. In effect, the decomposition of organic matter results in The use of some of the carbon, nitrogen, and some other elements by micro-organisms.
Read Also: Sources, Composition, Decomposition, and Mineralization of Soil Organic Matter and Soil Organisms
