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Prof. Brian Kronvang

Aarhus University, Denmark



“30 years of nitrogen management learnings from Denmark: a succesful turnaround and novel ideas for the next generation“

© Prof. Brian KronvangProf. Brian Kronvang
Copyright: privat

Abstract

Excess nitrogen (N) emissions to surface waters are a high priority environmental problem worldwide for protection of water resources in times of population growth and climate change. As clean water is a scarce resource the struggle for reducing nutrient emissions are an ongoing issue for many countries and regions. In Denmark, a wide range of national regulatory measures have been implemented since the mid1980s all with the aim to reduce land based N loadings of the Danish aquatic environment. These measures have addressed both point source emissions and especially also been devoted to reducing emissions from diffuse sources meaning from agricultural production. Common to the agricultural measures is that they until now are general, i.e. they have been applied uniformly everywhere irrespective of, for instance, geology and the natural nitrate reducing capacity in the subsoil and irrespective of the vulnerability of the receiving water body to eutrophication. Following nearly 3 decades of combating nutrient pollution our surface waters such as lakes and estuaries are only slowly responding on the nearly 50% reduction in N loadings achieved.


However, the implementation of the EU Water Framework Directive in Danish surface waters still call for further reductions of N loadings from especially diffuse sources. A new era of changing from national regulatory measures to targeted implemented measures was the outcome of a Commission on Nature and Agriculture established by the Danish Government in 2013. The Commission pointed to the need of increased agricultural growth along with an improved environment achieved through a more targeted and efficient regulation by applying advanced technological mitigation methods that have to be implemented according to the local attenuation capacity for nutrients in the landscape. As a follow up a national consensus model for N was established chaining existing leaching, 3D groundwater and surface water models that enable a calculation of the N dynamics and attenuation capacity within a catchment scale of 15 km2. Moreover, several research projects have been conducted to investigate the effect of a suite of targeted mitigation measures such as restored natural wetlands, surface flow and subsurface flow constructed wetlands, controlled drainage, buffer strips and intelligent buffer strips. Lastly, the Danish Government has in 2016 passed a new regulation of agricultural production allowing farmers to apply economic optimum levels of nitrogen to crops after nearly 18 years of regulation below economic optimum (1998: 10%; 2015: 21%).


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