Earthworm induced transfer of dung-carbon into soil particle size fractions

This study examined the role of earthworms in the stabilisation of soil organic carbon from livestock dung in a long-term mesocosm study, including its incorporation in deeper soil layers and association with particle size fractions. Two earthworm treatments were established, with the abundant and diverse treatment having 390 m⁻² less epigeic Lumbricus rubellus, 2400 m⁻² more endogeic Aporrectodea caliginosa and 220 m⁻² more anecic Aporrectodea longa at the final sampling than the treatment dominated by epigeic species. The abundant and diverse earthworm treatment increased the decomposition of dung in the surface 20 mm, and doubled the amount of dung-derived C within the <250 µm size fractions at 20–75 mm depth compared to the epigeic treatment (4.8 vs. 9.8 g/kg soil, respectively). Earthworms have the ability to increase sequestration of C into smaller, and potentially more stable, size fractions.