Reducing nitrogen losses is a federal priority under the nutrient reduction pathway (Art. 6a LwG) and groundwater protection (Art. 62a GSchG). The project aims to identify and quantify nitrate leaching risks in Switzerland and evaluate measures to reduce them. Experimental data from lysimeters and fields, combined with process-based models, assess mitigation effectiveness and underlying processes. Models allow results to be applied to other regions, optimize measure combinations, and evaluate climate change impacts. Findings will support practical agriculture and advisory services under Art. 62a.