نوع مقاله : پژوهشی
نویسندگان
1 استادیار بخش تحقیقات حفاظت خاک و آبخیزداری، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان فارس، سازمان تحقیقات، آموزش و ترویج کشاورزی، شیراز، ایران
2 دانشیار بخش تحقیقات حفاظت خاک و آبخیزداری، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان فارس، سازمان تحقیقات، آموزش و ترویج کشاورزی، شیراز، ایران
3 کارشناس ارشد بخش تحقیقات حفاظت خاک و آبخیزداری، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان فارس، سازمان تحقیقات، آموزش و ترویج کشاورزی، شیراز، ایران
4 استادیار بخش تحقیقات خاک و آب، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان فارس، سازمان تحقیقات، آموزش و ترویج کشاورزی، شیراز، ایران
5 دانشیار پژوهشکده حفاظت خاک و آبخیزداری، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction and Goal
Marl are porous rocks (with a porosity of 73% to 95%). Marl formations are highly sedimentary, and the different physical and chemical properties of marls affect the intensity and type of erosion. The form and intensity of water erosion are strongly influenced by changes in soil texture. Based on the results of previous research, the greatest correlation between marls and erosion intensity is related to their physical and chemical factors (particle distribution, especially sand particles). As the size of sand increases compared to silt and clay particles, gully erosion will also increase. The clay ratio index is decisive in the occurrence of gully erosion and the runoff volume index is decisive in the occurrence of surface and gully erosion of marls. On the other hand, there are significant differences in the measurements of sodium, magnesium, organic carbon content, pH, and SAR in the surface erosion, rill, and badland forms of marls. Marl soils are evolving materials whose inherent properties can be enhanced with additives and their use can be made possible. The establishment of vegetation on marls is also an important point, and the percentage of clay and gypsum in marls is closely related to the establishment of plants on marl soils. Thus, marls pose significant issues and problems related to use stabilization, construction, erosion, and sedimentation. Marl formations are widely distributed in the Maharlu watershed in Fars Province, indicating the watershed's high potential for erosion and sediment production, and understanding the characteristics of watershed marls is useful for use in soil conservation programs.
Materials and Methods
The Tang-e Sorkh and Bard-e-Kal watersheds, with an area of 500 hectares, are part of the Maharlu watershed and are located west of Shiraz. Almost the entire surface of these sub-watersheds is covered by the Gachsaran geological formation. Using geological map, topographic, slope and other available documentation, and observing erosional forms in the field, 11 marl soil samples were collected from a depth of 0–30 cm in three slope classes (less than 5%, 5 to 10%, and 10 to 20%). The electrical conductivity of the saturation soil extract (ECe), the acidity of the saturated soil mud (pH), the amount of calcium, magnesium, sodium, carbonate, chloride, bicarbonate, and organic carbon, cation exchange capacity, gypsum content, and the amount of equivalent calcium carbonate were measured. Analysis of physical and chemical properties of soil was performed based on the method of the Soil and Water Research Institute. Soil particle size was determined by hydrometer method, and soil texture was classified according to the USDA (United States Department of Agriculture classification) system. Statistical analysis of the data and determination of the effect of variables on the type of erosion were performed using the t-test with two independent populations. In addition, analysis of variance, principal factor analysis, and comparison of means were performed using Duncan's test (using SPSS statistical software).
Results and Discussion
The difference in the amount of equivalent calcium carbonate in the Tang-e Sorkh and Bard-e-Kal, regions was significant at the one percent level, and its amount in Tang-e Sorkh was much greater than in Bard-e-Kal. The difference in sand size was significant at the five percent level, with its size being greater in Bard-e-Kal than in Tang-e Sorkh. In the marls of the two sub-watersheds, the difference in acidity (pH) was significant at the one percent level, and it was higher in Tang-e Sorkh than in Bard-e-Kal. The sulfate content of Bard-e-Kal marls was much higher than in Tang-Sorkh, and this difference was significant at the five percent level. The amount of bicarbonate in the Bard-e-Kal marls was greater than in the Tang-e Sorkh, and this difference was significant at the five percent level. The different in the amount of equivalent calcium carbonate, gypsum, acidity, and calcium of marls in various erosional forms were significant at the five and one percent levels. Between the two regions in gully-eroded marls, the difference in ion exchange capacity and acidity was significant. The measurements of acidity, equivalent calcium carbonate, sodium ion, and clay percentage in Tang-Sorkh marls were higher than in Bard-e-Kal, and in other variables, the measurements were higher in Bard-e-Kal. In the two hydrological units studied, the highest and lowest organic carbon levels were observed in rill and surface erosion, respectively. In addition, the highest and lowest moisture content was observed in surface and rill erosion, respectively. The size of bicarbonate was also higher in rill erosion than other erosion forms. Determining the size of factors such as bicarbonate, equivalent calcium carbonate, gypsum, acidity and calcium ion, percentage of sand and total silt and clay were helpful in the occurrence of erosion forms. In the marls of the region, the high sodium absorption ratio (SAR) can lead to a greater dominance of surface and rill erosion compared to gully erosion. In the marls of the Gachsaran Formation, salinity was probably affected by the increase in gypsum size, and its role in intensifying erosion was reduced. The presence of more calcium carbonate in the Tang-e Sorkh watershed marls made them more stable, which was due to the greater inhibition of the effect of salinity and sodium. The percentage of water absorption of Tang-e Sorkh marls was higher compared to the Bard-e-Kal marls. Therefore, the ability of mass-type erosion movements was also higher in Tang-e Sorkh marls.
Conclusion and Suggestions
The results of this study showed that due to the characteristics of marls in the Maharlu watershed and their effective role on erosion and sedimentation special attention should be paid to them in local research. In this watershed, identifying the physical and chemical properties of marls, such as bicarbonate ions, calcium, sodium, salinity, and percentage of sand and clay, is important for controlling erosion and sediment deposition. As a result, for greater success of implementation plans in watershed management research, it is also necessary to pay attention to the role of characteristics such as chalk size in reducing salinity and the effect of acidity on the type of erosion. Based on the results of this study, it is suggested that for sedimentation management in the Maharlu watershed, vegetation cover and viable mulches should be used to stabilize the soil and sediment dams should be constructed. It is also suggested that GIS and remote sensing technologies be used to identify critical areas and develop water and soil resource management plans.
کلیدواژهها [English]
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