Within-field spatial distribution of ecosystem engineers such as earthworms determine the spatial patterns of important ecosystem processes at the field scale. But the driving factors that shape the within-field spatial variability of earthworm populations remain largely unclear. The aim of this study was to describe the earthworm distribution patterns in a tilled arable field and to explain earthworm spatial variability as a function of biotic interactions within populations and of abiotic soil heterogeneity measured as the soil apparent electrical conductivity (ECa).