SOLUBLE NITROGEN AND CARBON IN THE SUBSOIL IN RELATION TO VEGETABLE PRODUCTION INTENSITY
The amount of inorganic nitrogen (NO3-N + NH4-N) was between 500 and 2300 kg ha-1 N, mostly as nitrate. Based on the amounts of dissolvable organic carbon (DOC) we estimated the denitrification potentials from 500 to 1900 kg ha-1 NO3-N. There was no correlation between denitrification potential and amount of nitrate. Ammonium nitrogen was found mainly in the water saturated zone; the amounts of inorganic N were negligible.
The amount of sulphate in the subsoil was between 600 and 7000 kg ha-1 SO4-S. One subsoil contained up to 7000 kg ha-1 SO4-S due to the application of large amounts of ammonium sulphate in addition to potassium sulphate. In the other fields there was only a small correlation between S-input and S-amount in the subsoil.