Anaerobic digestion of animal slurries and plant residues is a valuable technology to produce bioenergy and fertilizers in organic farming systems, while at the same time reducing propagules of weeds and parasites in the input material. However, the digestion changes the quality of the slurry by reducing its content of organic matter and increasing mineral nitrogen (N) levels. This may have profound impact on soil fauna and microorganisms as well as the biogeochemical processes they drive. Organic farmers fear that application of digested materials may have negative implications for soil fertility by reducing the input of organic matter to the soil, compared to fertilizing with traditional animal slurries or green manures. Hence, it is important to gain knowledge about the short- and long-term effects on microflora and carbon (C) balance in soils fertilized with digested slurry
