Earthworm and enchytraeid activity under different arable farming systems, as exemplified by biogenic structures

A study was conducted in order to compare soil faunal activity in four experimental farming systems using different tillage, chemical input and crop rotation practices: A conventional system with deep-ploughing (CT), an integrated system with reduced tillage and minimum chemical input (IN), a system with reduced tillage and high chemical input (RT) and a system with minimum tillage and high chemical input (MT). In nine experimental fields with two sampling points each, earthworms were sampled and biogenic structures were identified and counted in topsoil profiles (0-14 cm depth). Components of these profiles were identified by morphological features. Quantitative analyses of these morphological features provided information about soil compaction, earthworm and enchytraeid activity and distribution of roots and crop residues in the soil matrix. The dominant species in the earthworm community was the endogeic Aporrectodea rosea. Earthworm densities were unexpectedly lowest under reduced tillage (6 specimens per m(2)), and highest under deep-ploughing (67 specimen per m(2)), the reverse effect being observed with enchytraeid worms, as ascertained by deposition of their faecal pellets in topsoil profiles. Strong very fine granular structure (STVFGR) was most frequent in the integrated farming system (IN). We concluded that in the studied site embracing four farming systems, enchytraeids play an important role in creating a stable soil structure and porosity at the low level of earthworm densities found in the integrated system (IN).