Session 7.5: Targeted drainage measures for improvement of water quality in Denmark
The reduction of nitrogen (N) and phosphorus (P) losses is not easily solved as the majority stems from agricultural diffuse sources. In Denmark, a new era of targeted agro-environmental nutrient regulation has been accepted as part of the Agricultural Package adopted by the Danish Parliament in 2016. Thereafter farmers were allowed to increase their fertilization to the economic optimum in exchange of implementing collective and targeted measures mitigating nutrient losses from fields. Targeted adoption of supplementary catch crops in areas where groundwater or estuaries waters are threatened by excess nitrate and where natural N removal in groundwater is reasonable low have been implemented as open calls for farmers. The collective measures include large schemes for wetland restoration, surface flow constructed wetlands targeting drainage losses, afforestation and taking organic soils out of production. To this end a new national program with catchment officers have been started with the aim to bridge farmers, municipalities and national agencies. Finally, an improved sub-catchment based targeted nutrient regulation will be adapted from 2019 and include new mitigation measures such as integrated buffer zones, subsurface flow constructed wetlands with biofilters, saturated buffer zones and controlled drainage which are all currently being tested in several larger innovation and research projects (BIOWATER, BUFFERTECH, MMM, SupremeTech, iDRAIN, InnoDrain). These research efforts are essential to know the processes that control their local effects for N and P, their relative importance over time, need for management and their cost-efficiency. The session will provide empirical evidence based on field investigation on the implications and effectiveness of different targeted mitigation strategies and new ways of assisting in finding local placement with farmers to facilitate a local adaptation.