SUBSOILS - CHEMO-DENITRIFICATION AND BIOLOGICAL-DENITRIFICATION, N2O AND N-2 EMISSIONS

Agricultural practices, soil characteristics and meteorological condit ions are responsible for eventual nitrate accumulation in the subsoil. There is a lot of evidence that denitrification occurs in the subsoil and rates up to 60-70 kg ha(-1) yr(-1) might be possible. It has also been shown that in the presence of Fe2+ (formed through weathering of minerals) and an alkaline pH, nitrate can be chemically reduced. Anot her possible pathway of disappearance is through the formation of nitr ite, which is unstable in acid conditions. With regard to the emission of N2O and N-2, it can be stated that all conditions whereby the deni trification process becomes marginal are favourable for N2O formation rather than for N-2. Because of its high solubility, however, an impor tant amount of N2O might be transported with drainage water.