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Perennial legume-grass leys and organic fertilizers are essential for soil fertility in organic farming. In stockless systems, inputs such as compost or biogas residues replace livestock manure, but their effects on soil fauna remain unclear. This study evaluated earthworm abundance, biomass and species composition in three farm types: mixed farm (MF) with two-year ley and two stockless organic systems with one-year ley cultivation, cash crop farm (CF) and soil fertility farm (SF; use of internal and external fertilizers after composting) within a field experiment in Germany. In each system, two treatments were investigated: (i) a fertilized treatment with system-specific nutrient inputs based on different utilization strategies of legume-grass mixtures, and (ii) a treatment without external organic fertilization, in which legume-grass biomass was largely mulched. Earthworms were sampled in spring and fall 2023 during clover or lucerne grass growth, and in fall 2024 after harvest of potatoes, using allyl isothiocyanate extraction. In spring and fall 2023, MF showed the highest earthworm abundance, particularly in regular mulched treatments, reaching up to 118 individuals m −2 , whereas stockless systems showed lower initial abundances (≤ 48 individuals m −2 ) but increased by fall 2023 (≤ 59 individuals m −2 ). After potato cultivation in fall 2024, earthworm abundance declined in MF and SF but increased in CF. Mulched treatments favored anecic species ( Lumbricus terrestris ), while compost fertilization supported endogeic species. Juveniles dominated most samples, indicating active reproduction. The results highlight the importance of continuous organic inputs and periods with soil rest for sustaining earthworm populations in arable systems. • Two-year vs. one-year legume-grass mixtures in the crop rotation boost earthworm abundance. • Following ploughing and potato cultivation largely eliminate positive effects of two-year legume-grass mixtures. • Mulching vs. cutting and removal of legume-grass mixtures increases earthworm abundance. • Compost application supports endogeic earthworm populations.
Möller et al. (Mon,) studied this question.