Variation of soil properties with sampling depth in two different light-textured soils after repeated applications of urban sewage sludge

Sarra Hechmi; Helmi Hamdi; Sonia Mokni-Tlili; Rahma Inès Zoghlami; Mohamed Naceur Khelil; Salah Jellali; Saoussen Benzarti; Naceur Jedidi

doi:10.1016/j.jenvman.2021.113355

Variation of soil properties with sampling depth in two different light-textured soils after repeated applications of urban sewage sludge

J Environ Manage. 2021 Nov 1:297:113355. doi: 10.1016/j.jenvman.2021.113355. Epub 2021 Aug 9.

Authors

Sarra Hechmi¹, Helmi Hamdi², Sonia Mokni-Tlili¹, Rahma Inès Zoghlami³, Mohamed Naceur Khelil⁴, Salah Jellali⁵, Saoussen Benzarti⁶, Naceur Jedidi¹

Affiliations

¹ Water Research and Technology Center, University of Carthage, P.O. Box 273, Soliman, 8020, Tunisia.
² Center for Sustainable Development, College of Arts and Sciences, Qatar University, P.O. Box 2713, Doha, Qatar. Electronic address: hhamdi@qu.edu.qa.
³ Arid Regions Institute, University of Gabès, Médenine, 4119, Tunisia.
⁴ National Institute for Research in Rural Engineering, Water and Forestry, P.O. Box 10, Ariana, 2080, Tunisia.
⁵ Center for Environmental Studies and Research, Sultan Qaboos University, P.O. Box 31, Al-Khoud 123, Muscat, Oman.
⁶ Lusail University, P.O. Box 9717, Jabal Thuaileb, Lusail City, Doha, Qatar.

PMID: 34375225
DOI: 10.1016/j.jenvman.2021.113355

Abstract

Semi-arid agricultural soils have increasingly been subjected to urban sewage sludge (USS) applications due to accelerated soil depletion and shortages in manure supply. Research studies addressing USS reuse have mostly been conducted in cropping systems and focused on changes in topsoil properties of a given texture. Therefore, sludge-soil interactions could be largely influenced by the presence of plants, soil particle composition and depth. In this field study, two agricultural soils (sandy, S and sandy loam, SL) received simultaneously four annual USS applications of 40, 80, and 120 t ha^-1 year^-1 in absence of vegetation. Outcomes showed the increase of carbon and macronutrients in both soils proportionally to USS dose especially in the topsoil profile (0-20 cm). Subsoil (20-40 cm) was similarly influenced by sludge rates, showing comparable variations of fertility parameters though at significant lower levels. The depth-dependent improvement of soil fertility in both layers enhanced the microbiological properties accordingly, with significant variations in soil SL characterized by a higher clay content than soil S. Besides, positive correlations between increases in sludge dose, salinity, trace metals, and enzyme activities in both soils indicate that excessive sludge doses did not cause soil degradation or biotoxic effects under the described experimental conditions. In particular and despite high geoaccumulation indices of Ni in both soils and profiles, the global concentrations of Cu, Ni, Pb, and Zn were still below threshold levels for contaminated soils. In addition, the maintenance of pH values within neutral range and the increase of organic matter content with respect to control would have further reduced metal availability in amended soils. Therefore, we could closely investigate the effects of texture and depth on the intrinsic resilience of each soil to cope with repetitive USS applications.

Keywords: Degradation; Fertility; Semi-arid soils; Soil depth; Urban sewage sludge.

MeSH terms

Agriculture
Metals, Heavy* / analysis
Sewage
Soil
Soil Pollutants* / analysis
Trace Elements*

Substances

Metals, Heavy
Sewage
Soil
Soil Pollutants
Trace Elements