Application of effluent from animal manure lagoons to cropland is an effective method of utilizing the nutrients in the effluent and minimizing groundwater and surface-water pollution. The objective of this study was to determine the effect of land application of effluent from a swine (Sus scrofa domenticus) manure lagoon on selected soil chemical properties at the end of an 11-yr study. Effluent was applied at rates to supply approximately 335, 670, and 1340 kg of N ha-1 yr-1 to ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] on a Paleudult soil from 1973 through 1983. Soil cores taken to a depth of 210 cm were analyzed for H2O-extractable NO3-N and Mehlich 1-extractable P and cations. Nitrate-N concentrations (1-5 mg kg-1) with the two lower rates were similar to concentrations where no effluent was applied. At the high effluent rate, NO3-N concentrations were elevated, particularly in the subsoil, and 540 kg NO3-N ha-1 was present in the profile. Phosphorus increased with loading rate and at the high rate, P concentrations (450 mg kg-1) in the 0- to 15-cm zone was 10 times the level above which no response to P fertilization would be expected. Potassium concentration increased with loading rate throughout the profile. Magnesium accumulation was inversely related to effluent loading rate in the 0- to 15-cm zone, but accumulation in the subsoil was directly related to loading rate. Comparison of profile nutrient distributions at the high rate for Years 6 and 11 showed no appreciable accumulation of NO3-N during the period. Accumulation of other nutrients during this 5-yr period was P, 210%; K, 200%; Ca, 140%; Mg, 60%; and Na, 10% as compared with Year 6. Soil pH was decreased by the high effluent rate but did increase from 4.2 at Year 6 to 5.0 at Year 11 due to the increased rate of application of basic cations during that period. The high rate poses a groundwater pollution hazard because of the large quantity of NO3-N present in the profile. In previous years, appreciable N was also present at the medium rate, but NO3-N was low at this rate in Year 11. The high P concentrations in the surface soil increase the potential for runoff transport of P, which might pose a surface-water pollution problem.
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