Background
• Nitrate leaching threatens both the environment and drinking water quality
• Switzerland ca. 380,000 ha with > 25 mg nitrate/L in groundwater (quality criteria for drinking water) [1]; the Gäu region (Canton Solothurn) is especially vulnerable
• Organic fertilizers (slurry, farmyard manure, etc.) might entail considerably increased leaching risks due to variable nitrogen (N) content and availability
• Aim: increase N use efficiency, simultaneously reduce leachin