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<p>The present experiment aims at investigating the medium-term effect of sewage sludge as an organic amendment to a degraded, saline soil in Central West Tunisia. The field research plot measures 4.22&#xa0;ha, and 5 t/ha of sewage sludge dry powder was applied. Soil and leaves samples were collected after six months of application and two years later to assess the immediate and medium-term effects of Sludge on soil quality, from the first layer of the soil horizon (0–30&#xa0;cm). Before the application, soil pH was neutral at about 8.0; since then, it has slipped towards 7.6. Electrical conductivity was already high (roughly 17.1 mS/cm) and climbed to 25.1 mS/cm in 2023. Organic matter rates were under 1%, later increased to nearly 2.1%, noticeably boosting fertility and soil structure. Phosphorus increased from 6.67 to 57.10 ppm. Water-holding capacity also improved, elevating from about 50% to 53–66% in 2023 and settling at 56.4% by 2025, so the soil keeps moisture longer. The mean concentrations of the heavy metals in the soil were in the following order: Fe &gt; Mn &gt; Pb &gt; Zn &gt; Ni &gt; Cd &gt; Cu. While the leaves were in the order of Fe &gt; Ni &gt; Mn &gt; Zn &gt; Pb &gt; Cu &gt; Cd. However, their post-application concentrations were well within limits and not harmful. The 2025 data indicate a stabilization, notably in Organic matter. Heavy metals in the soil showed stabilization or slight decrease, due to natural soil processes such as leaching, adsorption, or plant uptake. Continued monitoring is important in assessing bioavailability and mobility over time to ensure the sustainable use of Sludge in agriculture.</p> Graphical Abstract <p>The graphical abstract outlines a story of an agricultural plot with a measured area of 4.22&#xa0;ha, situated in a semi-arid region in the central west of Tunisia. The area was widely affected by climate change and the poor soil management practices, intensive agricultural practices (tillage), and the non-return of crop residues, leading to a depletion of organic matter. The farmer was open to changing traditional agricultural practices and agreed to try sewage sludge as an organic amendment. The field trial was conducted during 2023–2025. After proceeding with sludge treatment, the plot was treated with two doses of dry sewage sludge powder around 5t/ha. Soil samples were collected at 0–30&#xa0;cm depth six months and two years after sludge application. Results were promising after suldge application during the year of 2023, the improvement was mostly noted in organic matter amounts, heavy metals were higher but remained within limits. Additional analyses were done in 2025, showing a notable stabilization of all physicochemical analyses, mainly in organic matter, showing the potentiality of Sewage sludge as an amendment for immediate fertility, and mid-term organic matter conservation, notably in arid and semi-arid regions. However, careful monitoring is always advised.</p>

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Medium-Term Effects of Sewage Sludge Application on the Physicochemical Properties of Agricultural Soil and Crop Productivity in the Semi-Arid to Arid Region of Central-Western Tunisia

  • 期刊论文

  • 发表日期：

    2025年8月12日

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  • Farah Mlaiki,
  • Imene Dridi,
  • Ahlem Tlili,
  • Sondes Ben Hadj Mbarek,
  • Sana Dridi,
  • Rafla Attia

摘要

The present experiment aims at investigating the medium-term effect of sewage sludge as an organic amendment to a degraded, saline soil in Central West Tunisia. The field research plot measures 4.22 ha, and 5 t/ha of sewage sludge dry powder was applied. Soil and leaves samples were collected after six months of application and two years later to assess the immediate and medium-term effects of Sludge on soil quality, from the first layer of the soil horizon (0–30 cm). Before the application, soil pH was neutral at about 8.0; since then, it has slipped towards 7.6. Electrical conductivity was already high (roughly 17.1 mS/cm) and climbed to 25.1 mS/cm in 2023. Organic matter rates were under 1%, later increased to nearly 2.1%, noticeably boosting fertility and soil structure. Phosphorus increased from 6.67 to 57.10 ppm. Water-holding capacity also improved, elevating from about 50% to 53–66% in 2023 and settling at 56.4% by 2025, so the soil keeps moisture longer. The mean concentrations of the heavy metals in the soil were in the following order: Fe > Mn > Pb > Zn > Ni > Cd > Cu. While the leaves were in the order of Fe > Ni > Mn > Zn > Pb > Cu > Cd. However, their post-application concentrations were well within limits and not harmful. The 2025 data indicate a stabilization, notably in Organic matter. Heavy metals in the soil showed stabilization or slight decrease, due to natural soil processes such as leaching, adsorption, or plant uptake. Continued monitoring is important in assessing bioavailability and mobility over time to ensure the sustainable use of Sludge in agriculture.

Graphical Abstract

The graphical abstract outlines a story of an agricultural plot with a measured area of 4.22 ha, situated in a semi-arid region in the central west of Tunisia. The area was widely affected by climate change and the poor soil management practices, intensive agricultural practices (tillage), and the non-return of crop residues, leading to a depletion of organic matter. The farmer was open to changing traditional agricultural practices and agreed to try sewage sludge as an organic amendment. The field trial was conducted during 2023–2025. After proceeding with sludge treatment, the plot was treated with two doses of dry sewage sludge powder around 5t/ha. Soil samples were collected at 0–30 cm depth six months and two years after sludge application. Results were promising after suldge application during the year of 2023, the improvement was mostly noted in organic matter amounts, heavy metals were higher but remained within limits. Additional analyses were done in 2025, showing a notable stabilization of all physicochemical analyses, mainly in organic matter, showing the potentiality of Sewage sludge as an amendment for immediate fertility, and mid-term organic matter conservation, notably in arid and semi-arid regions. However, careful monitoring is always advised.