Nitrogen budget in the River Auli catchment: a catchment dominated by agriculture in southeastern Norway

• Published in: Ambio 1997-08, Vol.26 (5), p.289-295
• Main Authors: Hoeyaas, T.R, Vagstad, N, Bechmann, M, Eggestad, H.O. (Jordforsk, Aas (Norway))
• Format: Article
• Language: English
• Subjects: ABONOS NITROGENADOS; Agricultural land; Agricultural runoff; Agricultural soils; AZOTE; BASSIN VERSANT; COURS D'EAU; CROP YIELD; Crops; CUENCAS HIDROGRAFICAS; CURSOS DE AGUA; ENGRAIS AZOTE; ENVIRONMENTAL IMPACT; Forest soils; Grassland soils; IMPACT SUR L'ENVIRONNEMENT; IMPACTO AMBIENTAL; Intensive production; NITROGEN; NITROGEN FERTILIZERS; NITROGENO; NORUEGA; NORVEGE; NORWAY; Organic farming; POLLUTION BY AGRICULTURE; POLLUTION DE L'EAU; POLLUTION PAR L'AGRICULTURE; POLUCION DEL AGUA; POLUCION POR LA AGRICULTURA; RENDEMENT DES CULTURES; RENDIMIENTO DE CULTIVOS; RIVERS; WATER POLLUTION; WATERSHEDS
• ISSN: 0044-7447; 1654-7209

An intensive study on N inputs and losses has been carried out in six sub-catchments and the main catchment of the river Auli$(366\ {\rm km}^{2})$in southeastern Norway, from 1992 to 1995. Total N transport in the main river outlet was 20.6, 19.1 and 26.5 kg N ha-1yr-1, respectively, for the agrohydrological years 1992/93 to 1994/95. Approximately 85% of the total input of N to the catchment area is related to agricultural activities, of which 65-70% derives from mineral fertilizers. Only 15% derives from long-distance atmospheric deposition. Nitrogen input did not vary much from one year to another, while output varied considerably due to shifting weather conditions. Consequently, the surplus one particular year was mainly determined by the crop yields obtained. The whole catchment surplus varied from 20 to 41 kg ha-1during the monitoring period. High N surplus might increase the nitrate leaching risk, but other factors such as amount, intensity and time of precipitation, and net mineralization during winter appear to influence nitrogen losses to a great extent. The three-year average nitrogen transport from the agricultural catchment was 64 kg N ha-1yr-1. N transport from forest catchments was considerably lower and varied from 2 to 10 kg N ha-1yr-1. Agricultural losses were by far the most important contributor to N transport in the main river.