Field Response of Soil Physical Properties to Sewage Sludge
- Billie J. Lindsay * and
- Terry J. Logan
An anaerobically digested sewage sludge was applied to a Miamian silt loam (fine, mixed, mesic Typic Hapludalfs) at rates of 0, 7.5, 15, 30, 60, 90, 120, 150, 188, 225, and 300 Mg/ha. Surface soils (0–15) cm were sampled 4 yr after sludge application and analyzed for bulk density, particle density, porosity, saturated hydraulic conductivity, moisture retention, aggregate stability, shrinkage, liquid and plastic limits, and total C. Bulk density significantly decreased, and porosity, moisture retention at 5.9 kPa, 33 kPa, and 1.5 MPa, percentage water stable aggregates, mean weight diameter of aggregates, and liquid and plastic limits increased with increasing sludge application. Sludge application had no significant effect on particle density, available water, saturated hydraulic conductivity, and shrinkage. Physical property responses to sludge application were linear except aggregate stability and mean weight diameter of aggregates that showed a maximum effect at 60 Mg/ha sludge application rate. Organic C increased linearly with sludge application, and 4 yr after application there was three times as much C in the 300 Mg/ha plots as in the zero sludge control plots. It is likely that many of the observed differences in soil physical properties are due to effects of added organic matter and these effects have persisted for at least 4 yr.
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