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 rivers. Two case studies are presented, one from a sandy/organic soil, one from a peaty soil. Overall nitrogen retention was estimated by mass balance. Denitrification activity and plant biomass incorporation of nitrogen were used to complement and verify the mass-balance data. The study shows that artificial flooding of meadows did not contribute significantly to nitrogen retention in the introduced river water under the irrigation regimes utilized. The technique stimulated mineralization of the soil nitrogen pool to an extent which corresponded to the reduction of nitrate caused by denitrification. In the sandy/organic soil, denitrification was enhanced by the artificial flooding, while in the peat area the activity was lower than in a nonflooded reference area. Plant uptake of nitrogen was stimulated by flooding.