Improving the Ecological Performance of Miscanthus (Miscanthus x giganteus Greef et Deuter) through Intercropping with Woad (Isatis tinctoria L.) and Yellow Melilot (Melilotus officinalis L.)

Miscanthus is a promising high-yielding and low-input perennial biomass crop. However, as miscanthus does not produce nectar, it provides less support for pollinators than other perennial biomass crops, such as cup plant, Virginia mallow, or wild plant mixtures. This study discusses whether miscanthus could be intercropped with flower-rich biennial wild plants to further enhance its ecological functioning. In 2017, a demonstration plot was established in southwest Germany with two miscanthus intercropping regimes: woad (WAM) and yellow melilot (YAM). Both woad and melilot reached full bloom in 2018, the second year of cultivation. The flowering period of woad started and ended earlier than that of melilot. Woad remained harvestable until spring 2019, whereas the aboveground melilot was destroyed by brown hare in autumn 2018. However, the shed seeds of melilot reemerged homogeneously in 2019. The miscanthus developed better in YAM than WAM. This was most likely due to (i) stronger competition for water, nutrients, and light in WAM and (ii) nitrogen fixation advantage in melilot. These results indicate that the ecological performance of miscanthus could be improved by intercropping with melilot. Thus, we propose to further investigate the effects of intercropping on both the productivity and quality of miscanthus biomass.