The German government supports renewable energy production by fermentation of crops in biogas plants to significantly decrease national greenhouse gases emissions. According to EU Directive 2001/81/EC Germany has also to fulfil a reduction of ammonia emissions in the next years. Due to high ammonia contents biogas wastes are retransferred to agro-ecosystems as agriculture fertilizer. However, the knowledge of NH ₃-losses after field application of these slurries, in particular from mono-fermentation of crop biomass, is up to now rudimentary.