Stickstoffdüngewirkung und Stickstofftransfereffizienz von Düngemitteln auf Basis von Kleegrasbiomasse im Gefäßversuch mit Weidelgras (Lolium perenne)

The aim of our research was to compare the N fertilizer value of different clover-grass (CG) based fertilizers. A pot trial was set up with 8 treatments with Lolium perenne: fresh CG, ensiled CG, compost from CG, solid manure and liquid manure from dairy cows fed with CG, biogas digestate, an unfertilized and a mineral fertilizer control. Our hypothesis was that compared to composting, and to other treatments (e.g. silage) biogas digestates allow for a more efficient N fertilization due to a lower C/N ratio and a higher share of NH4 +. Dry matter yield, C/N ratio, N concentration, N release and Nitrogen use efficiency (NUE) were examined. The results show the highest overall NUE, N release and yield in the treatment with biogas digestate and the lowest in the compost treatment. The overall efficiency of a treatment approach was also influenced by the N transfer rates during the entire treatment chain. The short-term N fertilizer efficiency was mainly influenced by the characteristics of the amendments used, while the long-term N fertilizer efficiency is mainly influenced by the transfer factors during the chain harvesting treatment fertilization. In conclusion, any approach for a more efficient N use from the clover grass biomass-N should focus on reduction of N-losses while the chemical characteristics of the obtained fertilizer product is less relevant