FERTILIZATION EFFECT ON GASEOUS NITROGEN COMPOUND EMISSIONS IN THE MAIZE FIELD-PINE TREE FOREST SYSTEM OF THE LANDES-DE-GASCOGNE

Atmospheric chemistry depends on nitrogen compounds: NO and NO2 are tr opospheric ozone precursors, N2O is a greenhouse gas. A significant so urce for these compounds is the use of nitrogen fertilizer in agricult ure. Emissions of NH3, NO and N2O were measured on irrigated maize fie lds, after fertilization with urea or under pressure anhydrous ammonia , in the Landes de Gascogne. Nitrous oxide emissions were also observe d in winter. The imbalance of the nitrogen budget might be explained b y gaseous losses, water-table pollution remaining low. This is a speci ficity of this agrosystem.