Swine lagoon effluent was applied to soil for final treatment. The active soil profile appears to offer great potential as a final treatment media for partly treated animal wastes and cattle feedlot runoff. Effluent sprinkled on a grass-covered soil profile reduced COD, nitrogen, and phosphorous concentrations 79-95, 40-80, 95-99 percent, respectively over a 3-year period. Loadings ranged from 13.9 to 48.1 in. of lagoon effluent per May-October season. Removal of COD was attributed to biological activity and physical filtration in the upper inches of the soil. Phosphorus reduction resulted from chemical activity of the clay fraction near the soil surface. Nitrogen reduction was attributed primarily to denitrification deeper in the soil profile. The organic matter in the soil served as the carbon source for denitrification rather than the lagoon effluent. Organic matter content of the lower region of the soil profile was reduced and nitrogen removal by dentrification decreased. For disposal fields that are operated primarily for BOD removal, about 24 in. per year can be applied in most areas of Iowa. In areas where nitrate concentration in the percolate is of concern, applications should be limited to 600 lb/acre of nitrogen per season. (Author)