LAND APPLICATION OF POULTRY LAGOON EFFLUENT

Excess levels of plant nutrients are being applied to soils when efflu ent from waste treatment lagoons is repeatedly irrigated on small parc els of land adjacent to large poultry operations. Therefore, field res earch was conducted at College Station and Overton, Texas, to evaluate the effects of poultry lagoon effluent on soil, vegetation and surfac e runoff quality. Two cropping systems, bermudagrass and a bermudagras s/ryegrass rotation, and three application rates, 0, 538 and 1076 kg N /ha/yr, were studied in experimental plots 1.2 m wide and 2.4 m long, from February 1995 to April 1996. Each treatment was replicated three times in a modified random block design. The site located near College Station was on a Ships series clayey soil with a 0.5% slope. The sire near Overton was on a Bowie series fine-loamy soil with a 5.0% slope. Nutrient increases in the soil were directly related to effluent nutr ient levels and background soil concentrations. Nitrate and potassium concentrations significantly increased throughout the soil profile to a depth of 914 mm at the 1076 kg N/ha/yr rate at Overton. The 1076 kg N/ha/yr rate did not significantly increase yields on either crop syst em above the yields at the 538 kg N/ha/yr rate. The bermudagrass/ryegr ass crop was the most effective in nutrient uptake with 51% N, 43% P a nd 35% K taken up by the vegetation at the 538 kg N/ha/yr rate. Nutrie nt losses in the surface runoff were directly related to slope. Nitrog en losses in the surface runoff at the Overton site were three to five time higher than at the College Station site. However average nutrien t concentrations in the surface runoff at the two sires were similar w ith large standard deviations.