Combined effects of annual crop agricultural practices on earthworm communities

Earthworm communities are subjected to a great variety of agricultural practices in cropping systems. Most studies that focus on the impacts of agricultural practices on earthworm communities have been carried out on a small combination of practices (e.g., tillage, pesticides, fertilization...) while their simultaneous effects in the field remain little known. In this context, the aim of the present study was to jointly evaluate the effects of (i) tillage (ploughing vs reduced tillage), (ii) fertilization (mineral and organic) and (iii) pesticide applications (herbicides and a combination of insecticides, fungicides and molluscicides) on earthworm communities. Abundance, biomass and richness of earthworm communities were monitored for four consecutive years (2017 to 2020) on a network of 26 fields where annual crops are cultivated, in Brittany (France). The results of this medium-term multifactorial study highlighted that tillage was the most influential agricultural practice on earthworms, followed respectively by fertilization and pesticides application. Our study demonstrated that ploughing was more detrimental to earthworm biomass and richness than to earthworm abundance. Compared to reduced tillage, plough decreased earthworm richness by 1.2-fold, total earthworm biomass by 1.6-fold, Aporrectodea anecic biomass and abundance by respectively 2.7-fold and 2.8-fold. Increased mineral fertiliza-tion increased epigeic abundance and biomass as well as Lumbricus anecic biomass. In contrast, organic fertil-ization did not affect any earthworm community parameters. Increase use of insecticides, fungicides and molluscicides decreased the biomass of Aporrectodea anecic earthworms. Finally, endogeic earthworms have not been impacted by any agricultural practices. To move towards sustainable agriculture, it is necessary to adapt crop management in order to preserve the ecosystem services provided by soil biodiversity, in particular earthworms.