[Adjustment of nitrogen fertilization to the needs of plants and limitations posed by the risk of nitrate accumulation and pollution of the soil and subsoil].

In chalky Champagne, nitrogen balance is study to adjust availability to plant response. For this, it is necessary to know some parameters whose measurement is obtained progressively; plants exportation, nitrogen transformations in terms of transport processes in soil system, kinetic of mineralization of soil organic nitrogen, plants residus and agricultural waste waters. Lysimeters with rotation of Champagne (wheat, sugarbeet, potatoes...) are used to measure losses of nitrogen and follow transport of nitrates by mean of soil solution captors. Comparisons with field results, lysimeters results and laboratory experimentations are used to adjust an experimental model. Two examples show: 1) Nitrogen fertilizer requirement for wheat. 2) Possibility of maximum application for agricultural waste waters.