Effects of temporary grassland introduction into annual crop rotations and nitrogen fertilisation on earthworm communities and forage production

International audience; Earthworms contribute to a wide range of ecosystem services in agriculture. Most studies focusing on impacts of annual crop management on earthworm communities are related to soil tillage, fertilisation or pesticides, while the effect of introducing temporary grassland into an annual crop rotation remains largely unknown. In this context, the aims of the present study were to evaluate effects of (i) introducing grassland into a crop rotation, (ii) grassland duration and (iii) grassland fertilisation on earthworm communities and grassland forage production in a long-term experimental station in western France. Three years of highly fertilised (230 kg ha(-1) yr(-1) of mineral nitrogen) grassland preceded by three years of annual crop rotation was compared to an annual crop rotation without grassland and to six years of grassland either lightly (30 kg ha(-1) yr(-1) of mineral nitrogen) or highly (230 kg ha(-1) yr(-1) of mineral nitrogen) fertilised. Grassland introduction into a crop rotation significantly increased earthworm abundance, biomass, and diversity, especially for anecic species, and improved the functional structure of the earthworm community. Grassland duration and fertilisation increased earthworm abundance and biomass, especially for anecics, without affecting endogeic species and earthworm diversity. Grassland duration did not increase forage production, but the increase in fertilisation did. Three years of highly fertilised grassland significantly increased earthworm abundance and biomass, improved the functional structure of the earthworm community and produced as much forage per year as six years of highly fertilised grassland. Overall, the introduction of grassland into annual crop rotations appears an effective way to rapidly increase earthworm community parameters and, given the important role of earthworms in soils, enhance soil functioning.