NITROGEN-RETENTION IN ARTIFICIALLY FLOODED MEADOWS

Investigations of nitrogen retention in artificially flooded wetlands were performed in southern Sweden during 1991-1993. The purpose of the study was to investigate whether artificial flooding of meadows would be a possible means of reducing the nitrogen content in streams and r ivers. Two case studies are presented, one from a sandy/organic soil, one from a peaty soil. Overall nitrogen retention was estimated by mas s balance. Denitrification activity and plant biomass incorporation of nitrogen were used to complement and verify the mass-balance data. Th e study shows that artificial flooding of meadows did not contribute s ignificantly to nitrogen retention in the introduced river water under the irrigation regimes utilized. The technique stimulated mineralizat ion of the soil nitrogen pool to an extent which corresponded to the r eduction of nitrate caused by denitrification. In the sandy/organic so il, denitrification was enhanced by the artificial flooding, while in the peat area the activity was lower than in a nonflooded reference ar ea. Plant uptake of nitrogen was stimulated by flooding.