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Earthworm burrows of endogeic species ( Allolobophora caliginosa, Octolasium cyaneum) in artificially packed soil columns were examined using X-ray computed tomography. By means of digital image processing, it was possible to reconstruct and visualize the burrow system in three dimensions. The reconstruction revealed morphological features of the burrows which were not obvious from two-dimensional section images. [ABSTRACT FROM AUTHOR]

Column experiments were carried out to quantify the effect of earthworms on compacted soil. The earthworms ( Lumbricus terrestris) were able to burrow into soil which was artificially compacted to a pore volume as low as 40%; they may also penetrate an artificial 'plough pan' deep in the soil. The effect of the burrowing activity of Lumbricus terrestris was quantified by measuring hydraulic conductivities and infiltration rates through the whole soil column (19 cm wide, 40 cm long). Morphological parameters, mainly the vertically projected burrow depth, were correlated with the saturated hydraulic conductivity. The amount of casts deposited by Lumbricus terrestris on the soil surface increased with the degree of soil compaction. The bulk density of casts was always less than that of the original soil. [ABSTRACT FROM AUTHOR]