Facilitation of phosphorus (P) has been reported to occur in cereal/legume intercropping systems, but the underlying processes are still unknown. Such positive interactions may occur as a result of an increase of P availability induced by the roots of one of the two intercropped species, for the benefit of the companion crop. Enhanced mineralization of organic P as a consequence of an increase in acid phosphatase activity in the rhizosphere of the intercropped species is one of the processes likely involved in such facilitation. Our hypothesis was: acid phosphatase activities are different when plants are growing alone or when they coexist. To test this hypothesis, we used rhizoboxes, in which we finely mapped and monitored acid phosphatase activity weekly over five weeks for three treatments: chickpea and durum wheat, grown alone or intercropped. We used a novel non-destructive method for spatialized measurements of acid phosphatase activity, based on nitrocellulose membranes (16 x 30 cm), which were incubated for 3.5 hours against the soil, in order to sorb the enzymes. The soil used had not received P-fertilizers over 40 years, and was thus P-limiting for plants and microorganisms. Chickpea was able to create more hotspots of acid phosphatase activity than durum wheat. Interestingly, the cereal-legume intercrop was exhibiting more hotspots than chickpea, and thus did not show an intermediate behaviour, as expected in the absence of interaction. This supports the occurrence of P facilitation. Our approach thus proved efficient to study the spatial distribution of enzymatic activities, at the microscale, in the rhizosphere.