| Summary: | <List> <ListItem><ItemContent><p>● 0.98 Mg·ha<sup>−1</sup>·yr<sup>−1</sup> C<inf>org</inf> accumulation under miscanthus over 26 years.</p></ItemContent></ListItem> <ListItem><ItemContent><p>● C<inf>org</inf> accumulation under miscanthus continued even up to 26 years.</p></ItemContent></ListItem> <ListItem><ItemContent><p>● Reintegration of a miscanthus site into a crop rotation induced decreasing C stocks at first after 6 years.</p></ItemContent></ListItem></List></p> <p>Miscanthus× giganteus may play an important role in replacing fossil energy resources by bio-based alternatives. One further advantage of miscanthus production is the generally high soil organic carbon (C<inf>org</inf>) enrichment in soils. Due to declining yields, miscanthus stocks are commonly reintegrated into crop rotation after approximately 20 years. Currently there is only few information, whether these high amounts of C<inf>org</inf> can be conserved while intensifying soil tillage and crop management after reintegration. Therefore, we monitored C<inf>org</inf> stocks in a control with more than 20 years of continuous miscanthus and in a treatment with reintegration of a 20-years old miscanthus stock into an organic crop rotation. Based on δ<sup>13</sup>C soil values, we calculated an annual C<inf>org</inf> enrichment of 0.98 Mg·ha<sup>−1</sup>·yr<sup>−1</sup> C under miscanthus. More than 95% of the miscanthus-C was determined in the upper 0.25 m of soil. Continuing miscanthus cultivation did not affect yields during the first five extension years and C<inf>org</inf> stocks increased further. Following reintegration, C<inf>org</inf> stocks remained constant during five years, which was mainly attributed to the humification and/or stabilization of high amounts of destroyed roots and rhizomes. A significant decrease in C<inf>org</inf> (−5.7 Mg·ha<sup>−1</sup> C) compared to the continuing miscanthus cultivation was at first measured six years after reintegration into crop rotation, underlining the need of long-term investigations. Our data also show, that miscanthus production cycles can be extended in our region, and that sowing of the alfalfa grass mixture after rhizome/root destruction was efficient in preserving C<inf>org</inf> stocks for at least first five years after reintegration.
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