In 2016 the Danish parliament agreed that farmers were allowed to apply more fertilizer up to economic optimal level as a N quota before was regulated to be 10-18 pct lower this level. To counteract excess nitrogen leaching and load to waters, farmers were asked to implement targeted catch crops prioritized to catchments with too high load of nitrogen to coastal and marine areas. The effect of theses target catch crops is still not evaluated.

The purpose of this project is to improve the data and knowledge for future targeted emission-based nitrogen regulation. In the Danish future targeted emission-based nitrogen regulation, crop selection and cover of catch crops will also be included as a means of mitigation measure . It is important that the coverage and growth of catch crops and other measures are included in the nitrogen regulation, with effects that are realistic under practical and regional conditions. This is important in order to achieve the desired environmental effect and to ensure as cost-effective nitrogen regulation as possible.

The purpose of the project will be achieved by first determining the extent and growth of autumn vegetation for all fields and crops on the cultivation surface, including the targeted catch crops, in several catchments by utilizing the fact that satellite measurements have both detailed geographical coverage and high temporal resolution. Next, the development in catch crops will be compared to the trend in nitrogen loss to the water environment in a number of large and small catchments in the period 2015-2023.

• Work package 1:Analysis of the satellite images for autumn vegetation and detailed cultivation data, e.g. including sowing and plowing times obtained in the agricultural monitoring program. The response and knowledge for the satellite measurements will be transferred to catchments that do not have detailed sowing and plowing data but only include fields with names of the crops and areas with targeted catch crops. An algorithm will be developed for this.
• Work package 2: It will be examined whether areas with targeted catch crops in a catchment have had an effect on the trend of nitrogen loss to the aquatic environment. Both small, cultivated catchments and large coastal catchments will be analysed. Statistical analyses will be used for this.