Reduction of nutrient inputs through retention ponds

Tile drainage systems increase the possibilities for agricultural land use in many parts of the region. On the one hand, they enable intensive arable or grassland cultivation, and on the other hand, they represent the source of nearly half of the nitrogen inputs into regional waters. Therefore, the development of possible adaptation measures must in large part be focused on tile drainage systems.

The Leibniz-Centre for Agricultural Landscape Research (ZALF) is currently investigating options for reducing nutrient loads from tile drainage systems through appropriate retention measures. To this end, retention ponds with plant cover will be installed between tile drainage outlet and river system. Retention time, sedimentation processes, uptake of nutrients through biomass and biochemical transformation can together lead to significantly reduced nutrient emissions.

Under a sub-contract, ZALF will install a retention pond and regularly monitor the inputs and outputs in order to measure and analyse the actual retention of nutrients. A comparative analysis of the results of this retention pond with those from other locations which ZALF is monitoring will provide insights into the potential usage and effectiveness of this retention measure.

This project will provide the necessary practical information for the selection of optimal locations, the dimensioning, the costs of such applications, the prediction of necessary maintenance measures as well as the effectiveness in reducing nutrient loads into coastal waters. This information will be made available to possible stakeholders (farmers, water and soil associations). Water and soil associations will organize workshops with interested associations and farmers where the further implementation of measures will be discussed. Furthermore, the results of this project will facilitate the development of the MONERIS sub-model, which aims to quantify the potential of various measures to reduce nutrient loads through tile drainage systems. Local partners will use the retention pond beyond the duration of the project.