Positive effects of alternative cultural practices on terrestrial oligochaetes (clitellate annelids)
Résumé
Earthworms and enchytraeids are of great importance in soil agroecosystem functioning and are used as bioindicators in agricultural management. This study aimed at (1) understanding how the abundance and biomass of these soil organisms are affected by different cropping systems and cultural practices in two long-term experimental trials located near Paris, and (2) better defining the relationships linking earthworm and enchytraeid communities.
In Feucherolles, the trial compared fields with repeated inputs of fresh manure (MAN) or sewage sludges (SLU) with a system without organic fertilization (CONT). The other trial, in Versailles, compared four cropping systems, differing mainly in soil tillage, crop rotations, pesticide use and mineral fertilization: a conventional system (CONV), an integrated system (INT), an organic system (ORG), and a living mulch cropping system (LIV), with no ploughing and a permanent living cover crop. Earthworm and enchytraeid communities were sampled in spring 2014.
We found in average 114 and 177 earthworms m-² and 22 600 and 7 900 enchytraeids m-² in Feucherolles and Versailles, respectively. Organic matter inputs had a positive effect on earthworm density but no difference was found for enchytraeid density between the systems MAN, SLU, and CONT. In Versailles, earthworm density was not significantly different between the four cropping systems but it was between 1.5 and 2 times higher in the ORG and LIV systems than in the two others. We found a positive effect of LIV system on enchytraeid density, maybe due to the permanent plant cover. Enchytraeid density was between 2 and 3 times higher in the ORG system than in the INT and CONV systems. We thus found a positive effect of alternative cultural practices on the studied terrestrial oligochaetes. In Feucherolles, we found in average 1.9 times more biomass of enchytraeids than earthworms. This underlined the potential functional importance of enchytraeids in this trial. Finally, no significant correlation was found between enchytraeids and earthworms. In order to better understand the relationship between these soil organisms, more information should be collected at the species level.