Earthworm burrow number and vertical distribution are affected by the crop sequence of a grass-clover rotation system

Abstract Grass-clover is an important element in crop rotations due to its beneficial agronomic properties including nitrogen build-up, stimulation of earthworms and their burrowing and maintenance of soil macropores. We studied the relationship between important elements of grass-clover management in a crop rotation and earthworm diversity and macropore depth distribution, diameter and density from the ploughing layer to a depth of 1 m. Treatments included winter rye, 1st year cutting + slurry, 3rd year cattle grazing + slurry, 3rd year cutting + slurry and 3rd year cutting without slurry. The four-species earthworm assemblages and their burrow spatial structure responded distinctly to the temporal sequence of farming system management elements. The relative density of the endo-anecic and epi-anecic earthworm species, Aporrectodea longa and Lumbricus herculeus, was higher in the grass-clover phase of the rotation than under the annual crop, and increased with the age of grass-clover. The same was true for Aporrectodea rosea, but density and biomass of Aporrectodea caliginosa showed the opposite trend. Cattle grazing favours the occurrence of burrows (>5 mm ⌀) made by the anecics, A. longa and L. herculeus, while otherwise decreasing the number of fine-medium macropores (