Lumbricus terrestris middens are biological and chemical hotspots in a minimum tillage arable ecosystem

The biological (macrofauna and mesofauna), physical (size) and chemical (nutrient availability) properties of Lumbricus terrestris middens were studied on a minimum tillage field trial amended with farmyard manure, compost or unamended treatments. Results showed that herbivorous-type interactions with wheat crop leaves were common. Midden microhabitats containing these fresh leaves were significantly enhanced by up to 2.8-fold in mesofauna (springtails, enchytraeidae, mites, millipedes) abundance. Midden microhabitats on plots amended with farmyard manure had significantly (p < 0.05) more endogeic earthworms than compost amended or control plots. Further, middens found on farmyard manure amended plots were significantly (p < 0.05) larger, being twice the size (20.6 ± 1.7 g dry weight) of middens found on compost or control plots, demonstrating that farmyard manure improves midden microhabitat size and quality. Middens were enriched in extractable plant nutrients including P, K, S and Mn.