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

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Summary

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 one meter. 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 (<5 mm ⌀) below the topsoil. Our study reveals the intimate interdependence between the cropping sequence and the earthworm burrow structure with low number of detectable burrows under annual crops, then increasing in number during the grass-clover over 3 years. The highest number of burrows was found at 0.5 m depth in 3rd year cutting ± slurry, presumably because there is no soil disturbance by tillage in this horizon. The density of the endogeic A. caliginosa was negatively correlated with the presence of burrows and sensitive to grazing cattle compacting the topsoil. Positive correlations between burrows and density of L. herculeus indicate that this species was responsible for the burrows at one m depth while the density of A. longa was positively correlated with the burrows in the Ap horizon. We discuss the species composition in the grass-clover rotation system and its influence on soil ecosystem functioning.

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• Earthworm species and burrows related to agricultural management of clover-grass rotations. (deposited 19 Apr 2012 06:29)
  • Earthworm burrow number and vertical distribution are affected by the crop sequence of a grass-clover rotation system. (deposited 19 Apr 2012 06:24) [Currently Displayed]