Potential phosphorus leaching from sandy topsoils with different fertilizer histories before and after application of pig slurry

This study investigated the effects of historical long-term and recent single applications of pig slurry on phosphorus (P) leaching from intact columns of two sandy topsoils (Mellby and Boslid). The soils had similar physical properties, but different soil P status (ammonium lactate-extractable P; P-AL) and degree of P saturation (DPS-AL). Mellby had P-AL of 220280 mg/kg and DPS-AL of 3242%, which was higher than for Boslid (P-AL 140 mg/kg and DPS 21%). The study investigated the effects since 1983 of four treatments with different fertilizer histories, in summary high (HighSlurryMellby) and low (LowSlurryMellby) rates of pig slurry and mineral P (MinMellby) applications at Mellby and mineral P application at Boslid (MinBoslid). The columns were irrigated in the laboratory five times before and five times after a single application of pig slurry (22 kg P/ha). Concentrations of dissolved reactive P (DRP), dissolved organic P and total-P (TP) in leachate and loads were significantly higher (P < 0.005) from the treatments at Mellby than those at Boslid. TP concentrations followed the trend: HighSlurryMellby (0.570.59 mg/L) > MinMellby (0.410.49 mg/L) > LowSlurryMellby (0.310.36 mg/L) > MinBoslid (0.140.15 mg/L), both before and after the single slurry application. DRP concentrations in leachate were positively correlated with DPS-AL values in the topsoil (R2 = 0.95, P < 0.0001) and increased with greater DPS-AL values after the single slurry application (R2 = 0.79, P < 0.0001). Thus, DPS-AL can be an appropriate indicator of P leaching risk from sandy soils. Moreover, the build-up of soil P because of long-term repeated manure applications seems to be more important for potential P losses than a single manure application.