STUDIES ON THE INFLUENCE OF LONG-TERM MUNICIPAL SEWAGE-EFFLUENT IRRIGATION ON SOIL PHYSICAL-PROPERTIES

A study was conducted in a sewage farm of the Madurai Corporation to evaluate the effects of sewage-effluent irrigation over a period of 10-15 years on the soil physical properties when compared with soil irrigated with well water. The soil was sandy loam. Bulk density in the soils irrigated with well water by canals (S1) ranged from 1.32 to 1.58 mg cm-3, but in the sewage-irrigated soils up to 10 years (S2) the values were significantly lower up to 40 cm depth. The longer the period of sewage irrigation the less was the bulk density. The effect was seen up to 60 cm in the soil irrigated with sewage for 15 years (S3). The hydraulic conductivity, which was 9.1 cm h-1 in the canal-water irrigated soil, increased to 13.5 cm h-1 in S2 and to 16.5 cm h-1 in S3. Improvement in total porosity up to 66.9% over the control was observed in the sewage-irrigated soils. Stability index and aggregate stabilities were also improved by sewage irrigation.