INFLUENCE OF CUTTING FREQUENCY AND NITROGEN FERTILIZATION IN PERMANENT GRASSLAND ON THE BIOGAS PRODUCTION

摘要

In large regions of Europe grassland is not any more needed for fodder production because its use isnot economically viable. Because of the important role it plays in maintaining biodiversity and soil carbon storedgrassland should be maintained. The energetic use of grassland could be an alternative to generate income fromgrassland. A long term field trial was established in 1994 by sowing a mixture of 23 different grassland species andwas managed until 2007 under different nitrogen fertilizer levels regimes and cutting frequencies. Annual dry matteryields varied between 10.8 t ha~(-1) (2 cuts per year) and 9.1 t ha~(-1) (4 cuts per year). Energy- and CO_2-balances werecalculated to assess the energy efficieny and the global warming potential of different grassland managementsystems. Maximizing the overall biomass yields from grasslands does not always lead to maximized biogas yields,because these also depend on the quality (e.g. fibre content) of the harvested biomass. In conclusion, with regard toenergetic aspects, a high cutting frequency is favorable for maximizing biogas yields.