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 expe rimental farming systems using different tillage, chemical input and crop r otation practices: A conventional system with deep-ploughing (CT), an integ rated system with reduced tillage and minimum chemical input (IN), a system with reduced tillage and high chemical input (RT) and a system with minimu m tillage and high chemical input (MT). In nine experimental fields with tw o sampling points each, earthworms were sampled and biogenic structures wer e identified and counted in topsoil profiles (0-14 cm depth). Components of these profiles were identified by morphological features. Quantitative ana lyses of these morphological features provided information about soil compa ction, earthworm and enchytraeid activity and distribution of roots and cro p residues in the soil matrix. The dominant species in the earthworm commun ity was the endogeic Aporrectodea rosea. Earthworm densities were unexpecte dly lowest under reduced tillage (6 specimens per m(2)), and highest under deep-ploughing (67 specimen per m(2)), the reverse effect being observed wi th 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 st udied site embracing four farming systems, enchytraeids play an important r ole in creating a stable soil structure and porosity at the low level of ea rthworm densities found in the integrated system (IN).