- Title
- Soil erodibility indices affecting the development of gully erosion in highly erodible soils of the Tsitsa Catchment in T35D and T35E, Eastern Cape, South Africa
- Creator
- Kanuka, Gcobisa https://orcid.org/0000-0003-4736-7136
- Subject
- Soil erosion
- Subject
- River sediments
- Date
- 2022-01
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10353/22677
- Identifier
- vital:52642
- Description
- This study evaluated soil inherent properties for the development of gullies and their erodibility potential using the holistic field and laboratory sample investigation approach. The potential of negative impact of sedimentation on dam and water infrastructure performance has raised the need to evaluate the factors promoting soil erosion leading to land degradation. The study aimed to assess the relationship among the selected properties of soil and variability among various soil groups. A case study design approach was adopted at the T35D and T35E areas of Tsitsa hydrologic Basin, Eastern Cape, South Africa. The task was accomplished through detailed random soil sampling in the field, soil chemical analysis and comparative analysis of soil variables. Based on the scope of the study soil laboratory analysis included the following: particle size distribution, soil textural analysis, physicochemical parameters analysis, macro-and-micronutrient analysis, and micro-porosity analysis. Further spatial and scenario analysis of soil erodibility was done using selected erodibility indices such as Sodium Adsorption Ratio (SAR), Exchangeable Sodium Percentage (ESP), Dispersivity Ratio (DR), Clay Dispersion Ratio (CDR), Clay Flocculation Index (CFI), Water-Stable Aggregate analysis (WSA), and Soil Erodibility factor analysis (KEF). The findings of the study showed that the catchment hosts sixteen distinct soil forms categorized into seven unique soil groups. The results further indicated that the Katspruit soil form of the gleyic soil group has the highest clay-size particles and a considerably high clay dispersion attribute among others soil forms. It was further deduced that gleyic soil type exhibited the highest soil pH (6.36), a considerably low Ca:Mg ratio (1.43), a substantially high sodium ion (0.50 mg/kg), the highest SAR (0.5), lowest WSA (0.018percent) and a substantially high KEF (0.018ab). Similarly, saprolite soils exhibited the nature of the lixisol with a virtually equal amount of clay (43.63percent) and fine sands (41.68percent), the lowest amount of Ca:Mg ratio (1.35), the highest acid saturation (50.59), the highest ESP (8.39), and a considerably high WSA (38.75). Other remarkable problematic soils identified in the study include the lithic soil and the duplex soil. For instance, the Lithic soil is characterized by the highest fine sand-size texture (61.38percent), considerably low organic carbon (2.63percent), low cation exchange capacity (3.55 cmol(+)/kg), much high DR (0.75), very low WSA (0.027percent), and the highest KEF (0.027a). Whereas, the duplex soil is characterized by the highest DR (0.81), critically high CDR (38.19percent), very low WSA (0.019percent), and a considerably high KEF (0.019a). The relatively stable soils within the catchment are the oxidic, and melanic, where the WSA is highest in oxidic (38.19percent) and relatively high for melanic (36.6percent), CFI is highest in melanic (85.02percent), and oxidic (74.32percent), and KEF is relatively low (0.016b) for both. Correlation of the selected soil erodibility indices shows that CFI shares a perfect inverse relationship with CDR while maintaining a strong significant relationship with DR (R = -0.504). Findings also show that the SAR expectedly produced a robust significant relationship with ESP (R = 0.644), while KEF exhibited a solid inverse relationship with WSA (R = 0.913). The correlation across the physical and chemical properties suggests that DR and CDR can be firmly and positively influenced by dispersive clay. At the same time, the two factors maintain a significantly negative relationship with dispersive sand. Also, clay-sized particles depicted a significant relationship with WSA. Physicochemical and chemical parameters influence only the ESP and SAR. A remarkable finding is the influence of iron and its presence on SAR. On the other hand, ESP was distinguished from SAR due to the inverse influence of potassium. The lithic soils identify as members of the collapsible soil of South Africa, while the gleyic soils identify with duplex and saprolite soils in the class of dispersive soils. The vertic soils characterize as expansive soil, while the Duplex soil also exhibits a soft soil attribute. In general, the study suggests that T35D and T35E areas of Tsitsa catchment vary spatially in soil erodibility potential. T35D area is characterized by dominant oxidic soil cover of relatively stable aggregate whose iron oxide enrichment could be attributed to inculcation of dolerite debris. Overall, the soil erodibility indices showed that the development of gully erosion in Tsitsa catchment is driven by high clay dispersivity ratio of the soil (mean = 0.70; 24percent CV), and poor soil structure relative to the low WSA range (18.1 – 34.0). Erodibility due to high sodicity are associated with saprolite (ESP = 8.02) and gleyic soils (ESP = 7.43) while the high soil dispersion was due to the vertic (46percent), duplex (38percent), cumulic (30percent), and lithic (27percent) soil components. The poor soil aggregates (WSA) were mainly controlled by the lithic (10percent), vertic (27percent), duplex (28percent), cumulic (31percent), and gleyic (34percent) soil components. Meanwhile, the T35E area is dominated by the dispersive and collapsible soils dominated by saprolites and lithic soils. Therefore, the environmental stakeholders are advised to adopt the best management practices within the dam area considering the vulnerability of the catchment to the development of gullies and the potential impact of sedimentation on the adequate performance of Tsitsa dam and its water infrastructures.
- Description
- Thesis (MSc) -- Faculty of Science and Agriculture, 2022
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (76 leaves)
- Format
- Publisher
- University of Fort Hare
- Publisher
- Faculty of Science and Agriculture
- Language
- English
- Rights
- University of Fort Hare
- Rights
- All Rights Reserved
- Rights
- Open Access
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UFH Department of Agronomy
| Thumbnail | File | Description | Size | Format | |||
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| View Details Download | SOURCE1 | Kanuka G MSc UFH 2021 (1) (002).pdf | 1 MB | Adobe Acrobat PDF | View Details Download |