Immobilization processes generally do not take place when a legume crop, such as alfalfa or white clover, is plowed under. Mineralization will likely be the dominant process. Conversion processes of nitrogen to different forms are all accomplished by various groups and types of microorganisms found in the soil. Factors that affect microorganisms, such as temperature, oxygen supply and moisture, can affect the degree to which nitrogen conversions take place. Impact on water quality Both immobilization and mineralization processes can have a direct impact on water quality.
Immobilization can result in a reduction of inorganic forms of nitrogen, including nitrate.
However, this reduction in nitrate is generally temporary. Under favorable conditions, ammonium is further converted by microorganisms to nitrate. Buildup of nitrates in soil followed by heavy rains can move plant available nitrate below the root zone. Nitrate is a form of nitrogen that is highly mobile and easily moves with water. If depth to groundwater is shallow and the underlying soil is sandy, the potential for nitrates to enter groundwater is relatively high.