Appropriate agricultural practices can minimise the contribution that phosphorus (P) transfer from agricultural land makes to surface water eutrophication. Minimising P transfer by establishing riparian 'vegetated buffer strips' is becoming increasingly popular, as they have been shown to reduce total P delivery to streams. However, an uncertainty remains about how buffer strips alter the delivery of dissolved forms of P, which may be highly bioavailable to freshwater algae. The overall aim of this study was to investigate whether biological solubilisation processes operating within buffer strip soils can increase the risk of dissolved P transfer, and in turn, understand how better to manage them in order to minimise this. A soil survey across multiple established buffer strips showed that microbial biomass P contributes to elevated P solubility in buffer strip soils. A plot scale experiment measuring the quantity of P forms in runoff demonstrated that P remobilisation in buffer strip soils could result in increased delivery outputs of dissolved P, given the right rainfall-runoff conditions. A soil column leaching experiment showed that the growth of some common riparian grass species could increase P leaching due to enhanced carbon mobility in the soil. These results are contrary to the perceived role of plants, microorganisms and organic matter solely as sinks for dissolved P in riparian vegetated buffers strips. The acquisition of P during growth of plants and microorganisms and the release of P from biota, may lead to buffer strips increasing dissolved P transfer risk. Management of these biological pools and processes will be necessary if buffer strips are to retain dissolved forms of P. Harvesting and removal of the buffer strip vegetation could provide benefits by tightening the biological retention-remobilisation cycle of P in buffer strip soils.