Effects of Chia Seed Mucilage on Some Chemical and Microbial Properties of Soil under Drought Stress and Lead Pollution

Document Type : Research Article

Authors

Department of Soil Science, Faculty of Agriculture, University of Tehran, Karaj, Iran.

Abstract

Introduction
Soil degradation caused by the simultaneous occurrence of drought stress and heavy metal contamination is one of the most serious environmental challenges facing agricultural sustainability and ecosystem functioning, especially in arid and semi-arid regions such as Iran. Among heavy metals, lead (Pb) is particularly concerning due to its high persistence, non-biodegradability, and toxicity to soil organisms. Lead contamination disrupts soil biochemical processes, reduces microbial activity, and impairs nutrient cycling. These negative effects are intensified under drought conditions, which alter soil physicochemical properties and limit microbial functionality. In recent years, increasing attention has been paid to natural soil amendments that can enhance soil resilience under multiple stresses. Root mucilage, a gelatinous biopolymer secreted by plant roots, plays a vital role in improving soil aggregation, water retention, and creating a favorable microenvironment for rhizosphere microorganisms. However, due to the practical difficulties in collecting and manipulating natural root mucilage, chia seed mucilage has been proposed as a suitable natural analog and model system. The present study was conducted to investigate the interactive effects of low water stress and lead contamination on selected soil chemical and microbial properties and to evaluate the potential of chia seed mucilage as a soil amendment under these combined stresses. The main objective was to determine whether chia seed mucilage can mitigate the adverse impacts of drought and Pb on soil health.
Materials and Methods
This experiment was performed as a factorial completely randomized design (CRD) with three factors and three replications. The first factor was chia seed mucilage application at three levels (0, 0.3, and 0.6% w/w), the second factor was lead contamination at three levels (0, 150, and 300 mg kg⁻¹ soil) using lead nitrate (Pb(NO₃)₂), and the third factor consisted of two moisture regimes (field capacity as no-stress and low water stress). Soil was artificially contaminated with Pb and incubated for 4 months. Chia seed mucilage was extracted and uniformly mixed into the soil at the beginning of the experiment. Soil samples were then subjected to the respective moisture treatments for another 2 months. At the end of the incubation period, soil chemical properties including pH and electrical conductivity (EC) were measured. Biological properties, namely soil microbial respiration and microbial population, were also determined using standard laboratory methods. All data were subjected to analysis of variance (ANOVA) using SAS software, and means were compared by Duncan’s multiple range test at the 5% probability level.
Results
Low water stress significantly increased soil electrical conductivity and decreased soil pH, indicating changes in ion concentration and soil solution chemistry. Drought stress also caused a marked decline in microbial respiration and microbial population, highlighting the high sensitivity of soil microbial communities to water limitation. Lead contamination further intensified these negative effects. Increasing Pb concentrations (especially at 300 mg kg⁻¹) led to greater reductions in microbial activity and more pronounced disruptions in soil chemical balance. A significant synergistic interaction was observed between drought stress and Pb contamination, resulting in the most severe negative impacts on soil biological and chemical properties. Application of chia seed mucilage significantly improved soil conditions under both single and combined stress treatments. The 0.3% mucilage level was the most effective treatment, moderating the increase in EC, stabilizing soil pH, and notably enhancing microbial respiration and population compared to the control. This concentration effectively reduced the adverse effects of Pb and drought, likely through improved water retention, better soil structure, and decreased Pb bioavailability. In contrast, the 0.6% mucilage application showed weaker performance, suggesting that higher concentrations may not provide additional benefits and could potentially create less favorable conditions.
Conclusion
The findings of this study demonstrate that combined drought stress and lead contamination cause severe damage to soil chemical and microbial properties. However, the application of chia seed mucilage, particularly at 0.3% (w/w), can significantly mitigate these adverse effects by improving soil physicochemical conditions and supporting microbial communities. From a fundamental perspective, these results highlight the important ecological role of root mucilage-like substances in enhancing soil resilience under multiple environmental stresses. Moderate levels of mucilage appear to act as an effective natural amendment that improves water retention, stabilizes soil chemistry, and reduces heavy metal toxicity. This study suggests that the selection or breeding of plant species with higher root mucilage secretion capacity could be a promising, sustainable strategy for soil management in regions affected by drought and heavy metal pollution.

Keywords

Main Subjects

References

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Journal of Soil and Plant Science
Volume 36, Issue 2
March 2025
Pages 41-58

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