PHOSPHORUS RECOVERY IN SURFACE RUNOFF FROM SWINE LAGOON EFFLUENT BY OVERLAND-FLOW

A study was conducted in Alabama to determine P removal by overland fl ow of swine lagoon effluent on bermudagrass (Cynodon dactylon L.'Russe ll') and annual ryegrass (Lolium multiflorum Lam), Treatments included ammonium nitrate at 560 kg N ha(-1) yr(-1), three rates of lagoon eff luent which provided 560, 1120, and 2240 kg N ha(-1) yr(-1) and 71, 14 2, and 284 kg P ha(-1) yr(-1), respectively, and a control. Experiment s were conducted at 5 and 10% slopes on a Marvyn loamy sand (fine-loam y, siliceous, thermic Typic Kanhapludults). The length of slope from a pplication site do collection site was 6.1 m, Surface runoff was colle cted and sampled monthly for dissolved and sediment P, The results ind icated that higher concentrations of P were found during the early spr ing and summer seasons when treatments were applied. Concentrations of dissolved P and total P exceeded critical values associated with acce lerated eutrophication. No significant differences were found for sedi ment P concentrations on either 5 or 10% slopes for any of the three r ates of P application, Phosphorus applications did not significantly a ffect dissolved P concentrations an the 5% slope, but there were signi ficant treatment effects for dissolved P concentrations on the 10% slo pe, Slope did not significantly affect dissolved P concentration but s ignificantly affected sediment P concentration, Total P mass losses in surface runoff were < 0.6 kg P ha(-1) on the 5% slope and 1.0 kg P ha (-1) on the 10% slope during the research period.