Anecic earthworms and associated ecosystem services in a ley-arable crop rotation

Earthworms in general and anecic earthworms in particular, play a key role in the ecosystem service of water regulation through enhancing water infiltration and stimulating root growth to deeper soil layers by earthworm burrows. A crop rotation of grass and maize can be sustainable in terms of efficient nutrient use, but there is lack of information on the effect on earthworms. Earthworms were sampled over three years in a 36 years old experiment. Permanent arable land was compared with permanent grassland and with a ley-arable crop rotation. In the first year of arable cropping in the rotation, the number of earthworms was already low and not different from continuous cropping. In the three-year grass ley, the abundance of earthworms returned to the level of permanent grassland in the second year. The restoration of earthworm biomass took a minimum of three years. However, the anecic species did not recover in the three-years grass ley to the dominance they had in the permanent grassland. The number of earthworm burrows was related to earthworm biomass and was highest in permanent grassland. Our data suggest that anecic earthworms are under pressure in a ley-arable crop rotation, which may have a negative impact on the ecosystem service of water regulation.