Nitrogen losses

Usable nitrogen may be lost from soils when it is in the form of nitrate, as it is easily leached. Further losses of nitrogen occur by denitrification, the process whereby soil bacteria convert nitrate (NO3-) to nitrogen gas, N2 or N2O. This occurs when poor soil aeration limits free oxygen, forcing bacteria to use the oxygen in nitrate for their respiratory process. Denitrification increases when oxidisable organic material is available and when soils are warm and slightly acidic. Denitrification may vary throughout a soil as the aeration varies from place to place. The conversion of nitrate to gases causes nitrogen to be lost from the soil to the atmosphere. Denitrification may cause the loss of 10 to 20 percent of the available nitrates within a day and when conditions are favourable to that process, losses of up to 60 percent of nitrate applied as fertiliser may occur.[103] Ammonium volatilisation occurs when ammonium reacts chemically with an alkaline soil, converting NH4+ to NH3. The application of ammonium fertiliser to such a field can result in volatilisation losses of as much as 30 percent.