Soil bacteria that require air will rob nitrate nitrogen of its oxygen if there is not enough free oxygen in the soil to meet their demands. In this process, nitrate nitrogen is converted to gaseous forms of nitrogen, which then escape from the soil surface. The presence of undecomposed organic residues intensifies such losses in water-logged soils simply because such residues cause soil bacteria to be more active and use more oxygen. Although the first reaction of ammonium nitrogen is to be adsorbed onto the surface of clay and organic matter, it does not remain in the ammonium form very long under Kentucky s climatic conditions. It is transformed to nitrate nitrogen.
Nitrate nitrogen is subject to rapid loss from soil, either from leaching or from loss as a gas.
However, there is some indication that leaching of nitrate nitrogen is not as rapid in red soils as it is in browner soils. These reactions show that nitrogen can be used most efficiently by a crop if it is applied either while the crop is growing or just before it starts to grow. Even with these precautions, there will be occasions when split applications of nitrogen should be helpful. For example, heavy rains following applications of N can result in leaching losses from permeable soils or in denitrification losses in soils which tend to waterlog. Phosphate fertilizer, when applied to soil, reacts very rapidly to form compounds that are less soluble than the form in which the fertilizer was added.