Phosphorus is a key nutrient in crop production. A large fraction of soil P is however in mineral and organic forms, that are not directly and readily available for plants. Ecosystem engineers, like earthworms are deemed to modify the surrounding soil, both biologically and chemically. In the drilosphere, i.e. the soil volume that is influenced by earthworms, microbial activities have been often reported to be greater, resulting in enhanced enzymatic activities, thereby providing available nutrients for plants. Using rhizoboxes, we monitored acid phosphatase activity weekly over five weeks with endogeic earthworms (Allolobophora chlorotica) alone or with a chickpea / durum wheat intercrop. We employed a nitrocellulose membrane (16 x 30 cm), incubated for 3.5 hours against the soil, below the observation window, in order to sorb the acid phosphatase, and ultimately get a detailed map of its activity. The soil used had not received P-fertilizers for over 40 years, and was thus P-limiting for plants and microorganisms. The spatial distribution of hotspots of enzymatic activity was thereby measured at infra-millimetric scale, and assessed with geostatistics. Earthworms strongly enhanced the microbial activity in the bulk soil, without plant, with higher total areas of hotpots of acid phosphatase activity. In the presence of roots, earthworms seemed to concentrate the acid phosphatase activity in numerous little hotspots, which were generally co-located with earthworm casts.