Nitrogen can be converted directly to nitrates through lightning.
It can also be converted to ammonia (NH3) through free-living nitrogen fixing bacteria e.g <em>Azotobacter</em> or fixed on plants by symbiotic micro-organisms e.g <em>Rhizobium</em>. The Ammonia formed is converted to Nitrites (NO2) by nitrifying bacteria e.g <em>Nitrococcus</em> bacteria. The Nitrites are converted to nitrates by other nitrifying bacteria e.g<em> Nitrobactor</em>
Nitrification. The conversion of ammonium to nitrate is performed primarily by soil-living bacteria and other nitrifying bacteria. In the primary stage of nitrification, the oxidation of ammonium ( NH+4) is performed by bacteria such as the Nitrosomonas species, which converts ammonia to nitrites ( NO−2).
