During a complex investigation programme on the evaluation of the long‐term ecological impact of cropping Miscanthus, the substrate composition of residues in 4–8‐year‐old stands of Miscanthus × giganteus and the contribution of Miscanthus residues to soil organic matter (SOM) were investigated. Only about 50 % of the above‐ground biomass produced yearly was suitable for harvest because of pre‐harvest losses and harvesting residues. The potential supply to SOM was therefore 3.1 t ha−1 carbon annually accumulated by the litter, and 9.1 t ha−1 carbon accumulated by rhizomes and roots in the long term. These organic residues mineralized differently in laboratory experiments at generally high rates of decomposition. Analysis of soluble portions of the organic substance of these biomass components by hydrolysis with hot water, 2 % HCl and 80 % H2SO4 confirmed the results. Setting the SOM effect of an equivalent farmyard‐manure (FYM) supply to 100 %, Miscanthus residues reached 60 % (stubble, rhizomes), 80–90 % (pre‐harvest losses) and 100 % (roots). Established Miscanthus stands are able to produce about 8.2 t ha−1 organic substance, which is comparable with FYM in terms of SOM impact. This kind of calculation showed higher values for Miscanthus than for the agricultural crops investigated to date. An SOM increase of about 0.5 % on sandy soils and 0.2 % on silt soil was determined after 6–8 years of cropping Miscanthus × giganteus.

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Effects of 10 years of Miscanthus cultivation on different properties of mineral soil in North‐east Germany The effects of 4–10 years of Miscanthus cultivation on different soil properties was investigated at Klein Markow (Mecklenburg‐Pommerania, Germany) in variants with and without Miscanthus between 1994 and 2000. Soil containing Miscanthus showed higher concentrations of organic carbon (Corg) (+0,29 %) and total nitrogen (Nt) (+0,03 %) and consequently an increased storage of soil organic matter (SOM) (+15,5 t ha–1) as a result of high amounts of leaves, roots and rhizomes. With regard to concentrations of Corg, cation exchange capacity, porosity and water retention significantly increased, while the wet and bulk density decreased in Miscanthus variants. The concentration of Corg and storage of SOM were increased significantly during the experimental period of Miscanthus treatments. The mineralization of the organic soil compounds which developed was comparable with those of the SOM. The reintegration of the Miscanthus area into a crop rotation system was possible only after the last harvest in February and seed of winter rape in August of the same year. The application of Glyphosat and the later shading by rape stands led to failure of the Miscanthus cultivations.

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