SLUDGE APPLICATION EFFECTS ON RUNOFF, INFILTRATION, AND WATER-QUALITY

Land application of sewage sludge requires careful monitoring because of its potential for contamination of surface water and ground water. A rainfall simulator was used to investigate the effects of freshly ap plied sludge on infiltration, and on runoff of sediment and nutrients from agricultural crop lands. Rain was applied to 16 experimental fiel d plots. A three-run sequence was used to simulate different initial m oisture conditions. Runoff, sediment, and nutrient losses were monitor ed at the base of each plot during the simulated rainfall events. Slud ge was surface applied and incorporated at conventionally-tilled plots and surface applied at no-till plots, at rates of 0, 75, 150 kg-N/ha. Steady-state infiltrability increased as a result of sludge applicati on, although the no-till practice was more effective in increasing the infiltrability than the sludge application. No-till practices greatly reduced runoff, sediment, and nutrient losses from the sludge treated plots, relative to the conventional tillage practices. Incorporation of the sludge was effective in reducing nutrient yields at the convent ionally-tilled plots. This effect was more pronounced during the third rainstorm, with wet initial conditions. Peak loadings of nutrients ap peared during the rainstorm with wet initial conditions.