Monitoring the variation of soil quality with sewage sludge application rates in absence of rhizosphere effect

Soil Quality Assessment after 25 Years of Sewage Sludge vs. Mineral Fertilization in a Calcareous Soil

“…Among chemical indicators, those related to nutrients (N and P), EC, and pH, as well as trace metals, proved to be the most sensitive ones at 0-15 cm. The response of these indicators to SS addition and/or mineral fertilization was expected, and has been reported in many previous studies on the use of SS in agriculture [12,71,72]. In particular, the accumulation of trace metals with SS addition has been already reported and studied in this soil [10,73].…”

“…Other studies confirm this correlation [9,81] between exchangeable cations and pH, related to the increase in the amount of exchangeable cations, Na and K in this case, resulting from the leaching process, contributing to the pH acidification. As in most of the studies conducted on SS application [8,12,82], SOC and POM-C were seen to be highly sensitive to treatments at both depths [83]. In our study, however, an important observation was that while both SOC and POM-C revealed to be sensitive to the treatment, the proportion of POM-C over SOC was not.…”

“…In particular, the accumulation of trace metals with SS addition has been already reported and studied in this soil [10,73]. Changes in pH and EC have also been systematically reported in soils amended with SS, in contrast with MF or non-amended soils [12,74,75] and related to the content in soluble salts in SS (Table 1).…”

“…These correlations suggest that the addition of SS, which overall implied the addition of different accumulated doses of organic compounds, also implied an enrichment in P, trace metals, and, very likely, soluble compounds. Zoghlami et al (2020) [12] reported a concomitant change in SOC, P, and exchangeable Na with higher doses of SS application. A correlation between organic matter accumulation and an increase in EC has been also observed in similar studies [12,75].…”

“…Indeed, larger studies on the effect of different organic amendments on soil quality [11] observed that the overall effect can be positive, although some aspects, such as soil contamination or grain quality, may be compromised, depending on the type of amendment used. In particular, the consequences of SS application on soil chemical properties and the accumulation of contaminants have been extensively studied [5,12,13] and different strategies to minimize the risk associated with SS application have been developed [14].…”