Land Application of Sewage Sludge with Regard to Cropping Systems and Pollution Potential
1984
Higgins, Andrew J.
Aerobically digested liquid sewage sludge was applied to Sassafras sandy loam soils (Typic Hapludults), characteristic of the eastern coastal plain, for 3 consecutive years. Sludge was applied at rates of 0, 22.4, and 44.8 Mg of dry solids/ha in June of each year. Groundwater, soil, and crops were monitored for 4 yr to establish the effects of high rates of sludge application. The results indicate that sludge application of 22.4 Mg of dry solids/ha on Sassafras sandy loam soil, or other similar sandy loam soils, is the upper limit to ensure protection of the groundwater quality. Annual applications of sludge at 44.8 Mg of dry solids/ha resulted in gross contamination of the groundwater by NO₃⁻-N and other salts. However, no contamination of the groundwater by heavy metals was detected at either sludge loading rate. Fecal coliform levels were low throughout the duration of the study. Zinc and copper accumulated in the A soil horizon; however, no accumulation occurred in the B horizon. Corn (Zea mays) and rye (Secale cereale) yields were greatly enhanced by the addition of sludge but there was little difference in yield between the sludge loading rates. Uptake of heavy metals in the corn and rye occurred in response to sludge application. Zinc was the only metal that consistently appeared at levels above the control.
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