Some soil morphological effects of earthworm activity; field data and X-ray radiography.

Abstract

The effects of the burrowing activity of earthworms on recently reclaimed polder soils were studied in the field and by binocular microscopy and X-ray stereo-radiography. Most observations are from a plot in a grassed apple orchard, some from a permanent pasture. Species involved comprise Lumbricus terrestris, Allolobophora caliginosa, A. rosea, A. chlorotica and L. rubellus. Under grass cover, an A1 horizon is formed, increasing in thickness with time since introduction of the worm population. Under clean cultivated conditions and in strongly compressed wheel tracks, however, development of an A1 horizon is inhibited. The A1 horizon mainly consists of earthworm excreta, which fill most of the burrows. The pre-existing channel structure produced by roots is disrupted by the earthworms. The earthworm activity leads to a marked increase in air permeability of the surface horizon. This may not be sufficient explanation for the previously-reported yield increase of the orchard or the divergence in composition of the grass cover. Several kinds of burrows are distinguished by their shapes and contents, and ascribed to different species or genera. (Abstract retrieved from CAB Abstracts by CABI’s permission)