Biogas in organic agriculture: Effects on yields, nutrient uptake and environmental parameters of the cropping system

Summary in the original language of the document

System effects of biogas fermentation in organic cropping systems with and without livestock (dairy farming) were investigated from 2002-2005. In both systems no differences in yields and nutrient uptake were detected in the legume crops. In the livestock-system non legume crops of the slurry system had no higher yields but a higher nitrogen uptake (6 %) than the stable manure system. Slurry-fermentation had no effect on yields and nitrogen uptake. The inclusion of crop residues in the fermentation system increased the nitrogen uptake about by 10 % and reduced the nitrate leaching potential by ca. 10 %. The inclusion of external substrates lead to a further increase in nitrogen yield of 10 %, but to no significant increase in dry matter yields. Fermentation had no effects on P-availability of manures. In the stockless system fermentation of clover grass, straw and catch crops increased yields and nitrogen content of winter wheat by ca. 10 %, combined with a significant decrease in nitrate leaching potential (10 %) and in emissions of nitrous oxide (ca. 40 %).