6.3. Denitrification

The process that releases nitrogen back to the atmosphere is called denitrification. In this process molecular nitrogen is produced in nitrate reduction (Figure 6.2, R6.6, R6.7). This is the reverse process of nitrification: nitrates are reduced to nitrites ant then to ammonia. Denitrification is carried out by soil bacteria under both anaerobic and aerobic conditions. In soils with high organic matter content and anaerobic conditions, denitrification is more intense. The nitrogen produces in this process is emitted to the atmosphere, causing a loss for the soils. On local scale, this means the depletion of an important and frequently limiting nutrient, therefore denitrification is an undesirable process on managed lands.

NO3 → NO2 → NO + N2O → N2

(R6.6)

2 NO3 + 10 e + 12 H+ → N2 + 6 H2O

(R6.7)