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Dr. Gitte Blicher-Mathiesen

Aarhus University, Denmark

“Trends in the agricultural monitoring data and the contribution to evaluate measures in National Action Plans for the Aquatic Environment“

© Dr. Gitte Blicher-MathiesenDr. Gitte Blicher-Mathiesen
Copyright: privat


Monitoring of agricultural mini-catchments has been part of the Danish national monitoring programme (NOVANA) since 1989. Thus, nitrogen (N) concentrations and loads have been monitored in soil water, tile drains, and streams within five agricultural mini-catchments. The data from this monitoring provide data to evaluate the effects of mitigation measures implemented stepwise in the nine Danish action plans adopted so far to protect the aquatic environment

During the monitored period 1990/91-2014/15, the nitrate concentration decreased significantly from 22 to 12 mg N/L and from 32 to 16 mg in the soil water from loamy and sandy dominated catchments, respectively. In two loamy catchments, the annual flow-weighted total N concentration in tile drains decreased by 38 and 51%, and in the five streams monitored at the outlet of the five agricultural mini-catchments, it decreased significantly by 24 to 64%. The nitrogen surplus on agricultural fields at national level decreased by 40%, the decrease being most pronounced until 2003.

In the beginning of the monitoring period, mitigation measures were implemented to reduce the agricultural use of N in fertiliser and manure, mainly through better application times and techniques for the manure, and by making it obligatory for the farmers to submit fertiliser accounts to the Danish Ministry of Agriculture. Also, a levy system for not adhering to the regulations was introduced. To prevent N leaching during autumn and winter, the obligation to establish catch crops was raised stepwise to cover app. 4 to 14% of the agricultural area in the period 2000-2015. The enhanced use of catch crops has contributed to lower N leaching from the agricultural mini-catchment in recent years.

The experience gained from the Danish Action Plans for the Aquatic Environment clearly demonstrates that regulation of the utilisation of fertiliser and animal manure as well as catch crops is effective measures to reduce diffuse nitrogen emission from agriculture. However, it also demonstrates the complexity of defining an efficient regulatory system that considers individual needs and farming conditions. Finally, it confirms the need for an effective control body and an ongoing monitoring and evaluation programme.


Blicher-Mathiesen, G., Rasmussen, A., Rolighed, J., Andersen, H.E., Carstensen, M.V., Jensen, P.G., Wienke, J., Hansen, B. & Thorling, L. 2016. Landovervågningsoplande 2015. NOVANA. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 168 s. - Videnskabelig rapport fra DCE - Nationalt Center for Miljø og Energi nr. 205