Influence of urban sewage sludge amendment on agricultural soil parameters

Using sewage sludge for agricultural soil conditioning may be a potential alternative for its proper disposal and enhancing soil fertility by virtue of its high content of organic matter and several important plant nutrients. But the presence of toxic heavy metals and pathogens limits its use. Accordingly, the aim of this study was to assess the impact of different doses of sewage sludge (5, 10, 20, 30 and 50 t ha(-1)) on physicochemical and biological properties of sandy loam soil. It was observed that different soil parameters significantly changed according to the addition of different sewage sludge doses as compared to untreated control soil. Total organic carbon (TOC) and nitrogen (N) consistently improved up to the application of 50 t ha(-1) sewage sludge. Consequently, it led to a significant and rapid increase in soil microbial properties like microbial biomass, basal respiration and enzyme activities (alkaline phosphatase, dehydrogenase and urease) during the initial days of incubation, which gradually decreased up to 90 days. Sewage sludge also increased the Diethylenetriamine Pentaacetic Acid (DTPA) extractable available form of heavy metals (Ni, Cr, Pb, Cu and Cd). However, all values of available forms of heavy metals were below the threshold values for contaminated soil. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study demonstrated that different doses of sewage sludge significantly altered the physicochemical and biological properties of the soil, particularly enhancing levels of total organic carbon and nitrogen. Soil microbial properties rapidly increased during initial incubation, but gradually decreased after 90 days.