| چکیده انگلیسی مقاله |
Extended abstract
Introduction
Following the climate change of recent decades and the intensification of soil erosion and pollution, in many countries of the world, planting of a large area of Vetiver plant under the title of soil bioengineering has been considered for the protection of the environment and natural resources. Since Vetiver is a 4C plant, it has a high efficiency in energy conversion through photosynthesis. Its leaves and stems, when completely decomposed, create a compost containing brown, dark black and white materials. Vetiver compost has a high nutritional value for providing livestock fodder and a high biomass caloric value in the soil and microorganisms present in it. Among the important uses of Vetiver are soil protection due to its spreading and deep roots, use as fodder, plant purification properties, use of effective enzymes and hormones for soil maintenance on steep slopes, presence of active ingredients that can be used in the health, pharmaceutical and perfume industries, and its special feature in reducing CO2 (one plant can absorb 25% of excess carbon dioxide). Vetiver can be used as the most suitable protective wall on steep slopes of highways and side walls of dam reservoirs. By increasing the density of Vetiver roots in the soil, the degree of soil adhesion increases and the angle of internal friction of the soil decreases. It can be stated that the increase in the density of Vetiver roots is the reason for increasing the shear strength of the soil. Therefore, it is necessary to understand the performance of this plant for different environmental conditions. For this purpose, this research was conducted with the aim of better understanding the performance of this plant on the side slopes of the Sangar Dam reservoir in Siahkal County (Gilan Province).
Materials and methods
In this study, soil and Vetiver plant root sampling was carried out from a depth of 0-50 cm on the slope of the dam reservoir wall with different degrees of slopes of 30-40, 40-50, and 60-70 degrees in four replicates. A total of 12 untouched soil samples and 12 soil samples with Vetiver plant roots were sampled using steel rings and 12 Vetiver plant were sampled. Soil properties including soil texture using hydrometric method, soil moisture using gravimetric method, acidity using saturated mud method, electrical conductivity using extraction method and soil salinity with EC meter, organic matter, lime and potassium of soil were measured using film photometer in the laboratory. To investigate the effect of moisture and Vetiver roots on soil shear strength, laboratory direct shear measurement method was used. Vetiver root extracts were extracted separately by maceration method using methanol/water solvents (80/20) and the extracts were concentrated using a rotary device. Finally, the results of measuring soil properties, Vetiver root weight and plant root extracts were analyzed using ANOVA test, analysis of variance and comparison of means and SPSS software.
Results and discussion
Vetiver planting on the side slopes of the Sangar-Gilan Dam reservoir has been done with the aim of preventing soil erosion, stabilizing the slopes and riverside slopes. Vetiver plant roots vertically penetrate deep into the soil. The development of root hairs of the Vetiver plant increases with the increase in the slope of the soil. The weight of the tension wires increases in proportion to the increase in the slope of the soil. Therefore, the characteristics of the weight of Vetiver plant roots and the weight of Vetiver plant root extract are affected by the characteristics of soil in steep slopes. There is a significant correlation and relationship between the soil properties and the weight of Vetiver root (Chrysopogon zizanioides) and the weight of plant root extract in the steep slope of Sangar Dam. The results showed that the weight of the roots of this plant increases with the increase of biological activities. On the side slopes of the Sangar-Gilan Dam reservoir, the diameter and weight of the roots were measured from the first level with a slope of 30-40 degrees, the second level with a slope of 40-50 degrees and the third level with a slope of 60-70 degrees. It has increased from the soil surface to a depth of 20 cm. The diameter of Vetiver plant roots increased in the first level 1.5 mm, the second level 2 mm and the third level 2.1 mm. The development of these roots and its deadly threads has increased the shear resistance of the soil in the first level by 20.74%, in the second level by 22.28% and in the third level by 25.95%. The roots of the Vetiver plant have led to an increase in the adhesion of soil particles and prevented the movement and sliding of the soil downstream of the side slope of the Sangar-Gilan Dam reservoir.
Conclusions
The results of this research showed that, in addition to strengthening pastures, fodder production, and the possibility of aromatic and industrial use, Vetiver planting has increased the shear resistance of the soil on the slope. In fact, the establishment of this plant leads to an increase in adhesion and shear strength of the soil. It seems that the Vetiver plant (Chrysopogon zizanioides) has the ability to consciously recognize and adapt to the planted environment and changes the density and weight of its roots in accordance with the change of slope for better establishment. Therefore, by increasing the root density (RAR), the internal friction angle of the soil is reduced and it becomes intelligently compatible with the environment. Considering the development of the root system of vetiver plant up to several meters in sloping slopes, it is a good choice to increase soil adhesion, increase shear resistance, and by rooting deep into the soil, it leads to preventing soil erosion and landslides. . It is suggested to plant vetiver plant on steep slopes due to its high adaptability in different climates and conditions, the possibility of several meters of root growth, to stabilize the soil and prevent sliding and erosion on steep slopes. |