The air we breathe is composed of 78 percent nitrogen. Nitrogen can also be found in many varied forms in the soil. Plants need nitrogen from the soil for proper growth and development but are only able to use very specific forms of nitrogen. Plants cannot use the form of nitrogen found in the atmosphere. Natural biological process carried out by microorganisms in the soil convert organic nitrogen to inorganic forms, which plants are able to use.
Organic nitrogen is a common component in plant residues and organic matter.
Nitrate is the form of nitrogen that is most used by plants for growth and development. Where crops are grown, nitrates can also emanate from nitrogen fertilizers and manure. Nitrate, regardless of its source, is the form of nitrogen that can get into groundwater. Nitrate movement in the soil Unlike ammonium, nitrate does not attach to soil particles and, as a result, is easily moved by water. How nitrates move with water in the soil can be best illustrated by what takes place when soils become wet from rainfall.