Earthworms are sustained in a 116-year rye monoculture with ploughing by provision of soil organic carbon from farmyard manure

In arable fields, earthworm abundance declines with the level of intensification, due to soil disturbance and reduced food resources. In this context, continuous cropping of monocultures and removed plant residues are drivers for a decline in earthworm populations. Therefore, the earthworm communities of the 'Eternal rye', a 116-year field trial, were investigated. The Eternal rye was instigated in 1906 Vienna, Austria, mainly to compare the application of mineral fertiliser, farmyard manure (FYM) and no fertiliser application (unfertilised). A two-factorial design with factor fertiliser comprised of FYM, mineral fertiliser and unfertilised and factor crop rotation with levels crop rotation of winter rye ( Secale cereale L.) – spring barley ( Hordeum vulgare L.) – bare fallow) versus continuous cropping of winter rye. All plots were ploughed (25-30 cm) at the same time, after the application of FYM and before sowing of rye in late October. Earthworms were investigated for continuous rye and rye in crop rotation in April 2020-2022 by hand sorting. Results show that only fertilisation treatments impacted earthworm communities with highest total abundances under FYM (120 ± 92.9 m − 2 ) followed by mineral fertiliser (27.6 ± 21.4 m − 2 ) and unfertilised (9.55 ± 9.27 m − 2 ). The most abundant species was Allolobophora chlorotica under FYM and mineral fertiliser, followed by small numbers of Aporrectodea caliginosa , Aporrectodea rosea and Lumbricus terrestris . Interestingly, L. terrestris was observed only under FYM (2.69 ± 7.81 m − 2 ). Similar to earthworm parameters, soil organic carbon, NO 3 − -N and leaf area index were highest for FYM compared to mineral and unfertilised within and across cropping systems, while soil decomposition rate was highest for FYM only in continuous rye. The application of FYM compensated the effect of conventional management practices, such as monoculture and ploughing on earthworms and enhanced numbers of endogeic earthworm and L. terrestris compared to mineral and unfertilised treatments. • Lumbricus terrestris were only found in farmyard manure (FYM) across cropping systems. • All earthworm parameters were higher for FYM than mineral fertiliser or unfertilised. • Endogeic earthworm abundance was higher for crop rotation (CR) than monoculture (MC). • Soil organic carbon was highest for FYM and higher for MC than CR. • Litter decomposition rate was highest for FYM-CR and higher for CR than MC.