Four field sites which have been irrigated with various levels of secondary treated sewage effluent for 9 to 11 years have been examined for phosphorus content in soil water extracted with suction lysimeters. The cornfield site on Hublersburg clay loam irrigated with effluent had an average P concentration of 0.329, 0.070, and 0.046 mg/liter in soil water at 15, 60, and 120 cm respectively compared to 0.043, 0.046, and 0.037 mg/liter, respectively, under an adjacent fertilized, but unirrigated control. Year round application of effluent including 2 years of effluent plus sludge to reed canarygrass (Phalaris arundinacea L.) on Hublersburg clay loam resulted in average soil water concentrations of 0.170, 0.100, and 0.052 mg P/liter at 15, 60, and 120 cm, respectively.
In an abandoned field on Hublersburg clay loam where no P was removed by crops, P concentrations were 0.140, 0.103, and 0.076 mg P/liter for the treated plot and 0.038, 0.047, and 0.042 mg P/liter for the control at 15, 60, and 120 cm, respectively. Only the 15-cm depth had significantly higher P concentrations in the treated plot. A hardwood forest located on a Morrison sandy loam soil was irrigated year round. Phosphorus concentrations in soil water were 0.349, 0.080, and 0.087 mg/liter for the treated vs. 0.059, 0.039, and 0.039 for the control at 15, 60, and 120 cm, respectively. Leaching losses were calculated from concentration of P in soil water at 120 cm and from leaching volume which was rainfall plus irrigation minus potential evapotranspiration. Over all years of treatment no site had leaching losses of > 3% of the total applied.