Lumbricus terrestris regulating the ecosystem service/disservice balance in maize (Zea mays) cultivation

Background and aim Plant pathogenic and mycotoxin-producing Fusarium species are globally widespread and lead to large annual yield losses in maize production (ecosystem disservice). Systems with reduced tillage and mulching are particularly under threat. In the present study, the bioregulatory performance (ecosystem service) of the common earthworm species Lumbricus terrestris was analysed regarding the suppression of three economically relevant Fusarium species, and the reduction of their mycotoxins in the maize mulch layer, taking into account the size of maize residues. Methods A mesocosm field experiment was conducted in a reduced tillage long-term field trial on loam soil. Artificially Fusarium-infected maize residues of two size classes were used as a mulch layer. Impacts of the earthworm species on DNA amounts of Fusarium graminearum, F. culmorum, and F. verticillioides and concentrations of the mycotoxins deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), and zearalenone (ZEN) were analysed. Results The results reflect that Fusarium regulation by L. terrestris was species-specific and covered the whole spectrum from suppression (F. graminearum) to slight promotion (F. verticillioides). Regarding the mycotoxins, a significant acceleration of the degradation of all three toxins was detected. Fine chopping of the chaff (< 2 cm) did not significantly alter the earthworms’ regulatory capacity. Conclusion While L. terrestris can shift the ecosystem service/disservice balance in both directions with respect to Fusarium regulation, it shifts it towards ecosystem services with respect to mycotoxin degradation. In synergy with adapted agricultural management, this natural bottom-up effect can help to keep soils healthy for sustainable production in the long run.