Long-term yields and soil carbon sequestration from Miscanthus: A review

Abstract

Perennial rhizomatous grasses such as Miscanthus have been assumed to give sustainable biomass yields for at least 20 years, but there have been few productivity trials that have tested this assumption. In addition, it has been suggested that soil carbon sequestration increases linearly over time. Here, we review field trials of Miscanthus, established on former grassland and tilled land, that have been harvested annually for up to 20 years and changes in soil organic matter content have been measured. Yields of Miscanthus follow an establishment phase, a ceiling phase and then a phase of decline. The lengths of these phases are strongly influenced by climate, soils and management, but it is likely that Miscanthus plantations can produce commercially acceptable yield beyond 20 years. Net soil carbon sequestration depends on previous land use and is strongly influenced by the soil carbon stocks at the time of planting. Under Miscanthus a large fraction of the accumulated carbon is labile and would be rapidly lost if Miscanthus plantations were reconverted to cropland. Currently, it is not possible to derive a reliable default sequestration rate for land use change from cropland to Miscanthus energy crop.