Can industrial by-products enhance phosphorus retention within vegetated buffer strips?

Summary Using industrial by‐products (IBPs) in conjunction with vegetated buffer strips (VBSs) has the potential to be a cost‐effective strategy for tackling phosphorus (P) export from agricultural land. Using an integrated mesocosm approach, we examined the effect of surface application of IBPs within VBSs on the removal of P fractions in surface and sub‐surface flow. Artificial run‐off was applied to VBSs (1.2 m long × 0.4 m wide, and 5% slope) that were amended with either 20 t ha−1 of Al‐based water treatment residual (Al‐WTR) or 20 t ha−1 of ochre, or remained as unamended controls. To explore the persistence of the effects of amendment over multiple run‐off events, two 30‐minute artificial run‐off events (3 litre minute−1) were applied to the mesocosms over a period of five days. When compared with inflow concentrations, the unamended VBSs reduced total P (37–54%) and particulate P (61–64%) concentrations in surface run‐off, but increased soluble reactive P (SRP) (5–9%) and total dissolved P concentrations (4–8%). Enhancing VBSs with IBPs improved retention of soluble P fractions in surface run‐off, for example, 61–62 and 15–19% of the SRP in the inflow was retained in VBSs amended with Al‐WTR and ochre, respectively. Surface application of either ochre or Al‐WTR also reduced the concentrations of soluble P fractions in sub‐surface flow. The magnitude of these effects depended on inflow P concentrations. Unlike Al‐WTR, the effectiveness of ochre gradually declined over the duration of each run‐off event because of erosion of ochre by run‐off.