Nutrient and sludge assessment of dairy lagoons in central Texas

摘要

Increasingly rigorous regulations on land disposal of animal wastes require investigation of lagoon management practices to determine effective techniques to help meet land area requirements for field application. Twelve primary dairy lagoon celts under different management practices in three central Texas counties were evaluated for sludge accumulation and physiochemical characteristics. Samples comprised a supernatant and sludge mixture taken from the entire lagoon profile to simulate agitated lagoon material intended for land disposal. Analysis included pH, total solids (TS), volatile solids (VS), total Kjeldahl Nitrogen (TKN), and total ammonium-nitrogen (NH_4-N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), zinc (Zn), copper (Cu), manganese (Mn) and conductivity. Although strong statistical support linking treatment effectiveness and lagoon management practices was not found, some practices appear to influence the physicochemical properties of the slurry mix, including use of fresh flush water, separation of dry lot runoff, and increasing the number of treatment cells. TKN, K and P were linearly correlated to TS, indicating higher nutrient concentrations in the anaerobic lagoon sludge. The resultant elevated nutrient levels in the slurry mix, compared to supernatant values, will require greater land area to meet PorN crop requirements. Land applying a lagoon slurry mix will require two and a half and four times as much land area than expected using published supernatant values for P- and N-based application rates, respectively. Consideration of best management practices (BMPs) may be advised to alleviate lagoon cleanout and sludge disposal challenges.