PO 46: Describe environmental effects from nutrient loss by:

Volatilization is the loss of nutrients in the gas form.  Urea nitrogen (found in urea fertilizer, UAN solution fertilizer, and manure) is unique in that the available ammonium N (NH₄⁺) from urea can be rapidly converted to ammonia (NH₃), which is a gas.  If this reaction occurs on the soil surface, the ammonia is lost into the atmosphere.  Losses of over 1/3 of the N from urea can occur within one week of surface application of a urea-containing material.  Tillage or ½ inch of rain, which incorporates the urea, will minimize this loss.  The sooner tillage or rain occurs after application, the smaller the losses will be; thus immediate incorporation or timing application just before rain are important to reducing this loss.  Other common N sources, such as ammonium sulfate and ammonium nitrate, are not susceptible to volatilization loss.  Also, urease inhibitors have been developed as an additive to urea to effectively reduce this loss when incorporation is not possible.  Volatilization can represent a significant loss to the crop and the ammonia that goes into the atmosphere represents a significant potential pollution problem.

Denitrification is the loss of gaseous forms of N due to anaerobic conditions, like when soils become saturated with water.  This is especially a problem in poorly-drained soils.  Denitrification occurs when all organisms in a saturated soil begin to run out of oxygen.  Some of these organisms have developed the ability to extract the oxygens from nitrate (NO₃^-) to survive.  In the process, the N from the nitrate is released as either dinitrogen (N₂) or nitrous oxide (N₂O), both of which are gases which are unavailable to plants.  Nitrous oxides are greenhouse gases with serious environmental implications.