Volume 19, Issue 2 (7-2025)
مرتع 2025, 19(2): 144-160 |
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Increasing Soil Stability in Degraded Rangelands Using Humic Substances (Case Study of the Soil of Taghazi Sangelands in Zabol County). مرتع 2025; 19 (2) :144-160
URL: http://rangelandsrm.ir/article-1-1276-en.html
URL: http://rangelandsrm.ir/article-1-1276-en.html
Abstract: (490 Views)
Background and objectives: The rangelands of the Sistan region are highly susceptible to wind erosion due to low rainfall, low soil organic matter, sparse vegetation cover, and the persistent 120-day seasonal winds. Wind erosion in this area has resulted in numerous adverse effects, including reduced visibility leading to traffic accidents, negative impacts on human health, soil loss, and a decline in the productivity of agricultural lands. Therefore, strategies to enhance soil resistance to wind erosion are critical. This study aimed to evaluate the effect of humic substances on improving soil stability in degraded rangelands of Taghzi, Zabul.
Methodology: A factorial experiment was conducted using a completely randomized design with three replicates. The first factor was soil sensitivity to wind erosion, classified into three levels: low sensitivity (S1), medium sensitivity (S2), and high sensitivity (S3). The second factor was the application of humic substances in two levels: with humic substances (H1; a combination of humic acid and fulvic acid) and without humic substances (H0). Humic substances were applied once through irrigation; the quantity supplemented to each pot was calculated based on the soil content and mixed with 200 ml of water. Control treatments received only 200 ml of water. After three months, the following parameters were measured: soil pH, electrical conductivity, calcium carbonate (lime) percentage, organic matter content, total nitrogen percentage, soil microbial respiration, microbial population, soil stability (expressed as the weight percentage of soil aggregates retained on wet and dry sieves), and the mechanical resistance of wet soil. Data were tested for normality and homogeneity of variances prior to analysis using ANOVA in Statistix 10 software. Means were compared using the LSD test at a 5% significance level.
Results: Application of humic substances in highly sensitive soils (S3) resulted in the highest calcium carbonate content (37.17%), microbial respiration rate (0.14 mg CO₂ g⁻¹ soil day⁻¹), and nitrogen concentration (0.33%). Conversely, the lowest calcium carbonate level (19.50%) was found in low sensitivity soil (S1) treated with humic substances. Soils without humic application showed minimal microbial respiration (0.03 mg CO₂ g⁻¹ soil day⁻¹) across all sensitivity levels. Nitrogen content was lowest (0.03%) in medium sensitivity soils (S2) without humic substances. In terms of soil aggregate stability, the highest percentage of dry soil aggregates retained on the 11.2 mm sieve was recorded in highly sensitive soil treated with humic substances, whereas medium sensitivity soils exhibited the greatest dry aggregate retention on the 2 mm sieve. For wet sieving, maximum aggregate retention in the 11.2 mm and 8 mm sieves was observed in highly and medium sensitive soils with humic treatment, respectively. Humic substances also led to the largest increase of wet aggregates in low sensitivity soils on the 4.75 mm sieve. The greatest retention of wet aggregates in the 1.8 mm sieve occurred in highly sensitive soils. Overall, soils without humic treatment exhibited the lowest wet aggregate stability. The mechanical resistance of wet soils increased significantly with humic application, especially in medium and low sensitivity soils.
Conclusion: This study demonstrated that the application of humic substances significantly improved the physical and chemical properties of degraded rangeland soils, enhancing nitrogen content and microbial respiration which fosters a more active soil microbial community. Compared to chemical fertilizers, humic substances represent an accessible and environmentally sustainable soil amendment that can effectively increase soil stability, particularly in soils vulnerable to wind erosion. The cost of using humic substances is generally minimal relative to the extensive economic and environmental damages caused by wind erosion, such as reduced soil fertility, vegetation loss, increased restoration expenses, and ecological risks. However, region-specific economic analyses are recommended to optimize decision-making and promote this practice for sustainable rangeland management.
Methodology: A factorial experiment was conducted using a completely randomized design with three replicates. The first factor was soil sensitivity to wind erosion, classified into three levels: low sensitivity (S1), medium sensitivity (S2), and high sensitivity (S3). The second factor was the application of humic substances in two levels: with humic substances (H1; a combination of humic acid and fulvic acid) and without humic substances (H0). Humic substances were applied once through irrigation; the quantity supplemented to each pot was calculated based on the soil content and mixed with 200 ml of water. Control treatments received only 200 ml of water. After three months, the following parameters were measured: soil pH, electrical conductivity, calcium carbonate (lime) percentage, organic matter content, total nitrogen percentage, soil microbial respiration, microbial population, soil stability (expressed as the weight percentage of soil aggregates retained on wet and dry sieves), and the mechanical resistance of wet soil. Data were tested for normality and homogeneity of variances prior to analysis using ANOVA in Statistix 10 software. Means were compared using the LSD test at a 5% significance level.
Results: Application of humic substances in highly sensitive soils (S3) resulted in the highest calcium carbonate content (37.17%), microbial respiration rate (0.14 mg CO₂ g⁻¹ soil day⁻¹), and nitrogen concentration (0.33%). Conversely, the lowest calcium carbonate level (19.50%) was found in low sensitivity soil (S1) treated with humic substances. Soils without humic application showed minimal microbial respiration (0.03 mg CO₂ g⁻¹ soil day⁻¹) across all sensitivity levels. Nitrogen content was lowest (0.03%) in medium sensitivity soils (S2) without humic substances. In terms of soil aggregate stability, the highest percentage of dry soil aggregates retained on the 11.2 mm sieve was recorded in highly sensitive soil treated with humic substances, whereas medium sensitivity soils exhibited the greatest dry aggregate retention on the 2 mm sieve. For wet sieving, maximum aggregate retention in the 11.2 mm and 8 mm sieves was observed in highly and medium sensitive soils with humic treatment, respectively. Humic substances also led to the largest increase of wet aggregates in low sensitivity soils on the 4.75 mm sieve. The greatest retention of wet aggregates in the 1.8 mm sieve occurred in highly sensitive soils. Overall, soils without humic treatment exhibited the lowest wet aggregate stability. The mechanical resistance of wet soils increased significantly with humic application, especially in medium and low sensitivity soils.
Conclusion: This study demonstrated that the application of humic substances significantly improved the physical and chemical properties of degraded rangeland soils, enhancing nitrogen content and microbial respiration which fosters a more active soil microbial community. Compared to chemical fertilizers, humic substances represent an accessible and environmentally sustainable soil amendment that can effectively increase soil stability, particularly in soils vulnerable to wind erosion. The cost of using humic substances is generally minimal relative to the extensive economic and environmental damages caused by wind erosion, such as reduced soil fertility, vegetation loss, increased restoration expenses, and ecological risks. However, region-specific economic analyses are recommended to optimize decision-making and promote this practice for sustainable rangeland management.
Type of Study: Research |
Subject:
Special
Received: 2024/07/27 | Accepted: 2025/06/28 | Published: 2025/07/1
Received: 2024/07/27 | Accepted: 2025/06/28 | Published: 2025/07/1
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