Which process involves the oxidation of ammonium compounds in dead organic material into nitrates and nitrites?

• A. Denitrifying Bacteria
• B. Population
• C. Nitrogen Fixing Bacteria
• D. Nitrification

Answer: (D)

Nitrification is the microbial oxidation of ammonium compounds released during the decomposition of dead organic material, first to nitrite and then to nitrate. This two-step process happens under aerobic conditions and involves distinct groups of microbes: ammonia-oxidizing organisms convert ammonium to nitrite, and nitrite-oxidizing organisms then convert nitrite to nitrate. The result is a form of nitrogen that plants can take up, though in some environments nitrate can be lost by leaching or, in low-oxygen zones, by denitrification back to gases. This distinguishes nitrification from denitrifying bacteria (which reduce nitrate to nitrogen gas) and from nitrogen-fixing bacteria (which convert atmospheric N2 into ammonia), and it isn’t simply a population phenomenon.