This review comprises a general description of nitrogen in soil water and the use of nitrogen fertilizer. The following investigations on nitrogen leaching and transformations are described: Investigations on drainage water. Losses of nutrients by leaching in agricultural production. Influence of nitrogen fertilizer on nitrate nitrogen content in drainage water.

Nitrate reduction in the subsoil.

Water balance and nitrogen balance by optimum plant production.

The main conclusions are that the leaching of nitrogen as nitrate mainly occurs in the autumn and winter periods as a result of biological degradation of plant residues. Increased plant covering of the soil will decrease the nitrate leaching.