review questions

Nitrification is a biological oxidation of ammonium to nitrite and the oxidation of nitrite to nitrate. The 1st step of nitrification is carried out by bacteria Nitrosomonas sp. (under aerobic conditions). Nitrosomonas is a chemo-autotroph which utilizes energy released during oxidation, and synthesize their organic matter from carbon dioxide. The second step of nitrification is carried out by a chemo-autotroph bacteria Nitrobacter for the same reason - it uses energy and C released during oxydation.

Nitrification acidifies the soil, since it yields nitric acid, with 2 hydrogen ions tending to be produced for every ammonium ion nitrified:

NH4+ + 2O2 = NO3- + 2H+ + H2O

and the fact that H+ ions are released in this reaction explains the acidification of the soil