نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 دانشجو دکتری ،گروه علوم خاک دانشگاه علوم کشاورزی و منابع طبیعی گرگان، ایران
2 استاد ، گروه علوم خاک دانشگاه علوم کشاورزی و منابع طبیعی گرگان،ایران
3 دانشیار، گروه علوم خاک دانشگاه علوم کشاورزی و منابع طبیعی گرگان،ایران
4 دانشیار، گروه زمین شناسی دانشگاه گلستان، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction: Loess soils are a special type of silty soils with a porous structure and weak adhesion. In case of improper management, loess soils are the most sensitive soils to erosion and are easily washed away by heavy rains. One of the most important influencing factors in the vulnerability of loess soils is the phenomenon of dispersion. during which the soil floats in it as a result of contact with water and is removed from the environment by the force of the water flow. Many studies have been conducted by researchers to investigate dispersive soils. Providing a suitable improvement method for them requires the correct determination and diagnosis of the degree of divergence in the studied area. The complete identification of dispersive soil also depends on a detailed test. As a result, various methods have been presented to identify soil dispersion. The most significant of which are the pinhole, chemical, crumb and double hydrometry methods. So far, there is no general consensus regarding prioritizing the use of dispersion tests. Considering the importance of the issue of divergence on the quality of soil and agricultural products, in this research we try to investigate the accuracy of different tests in detecting soil dispersion.
Materials and Methods: This research was focused on loess soils of Golestan province. seven pedons were selected, sampled and described in different parts of the province. Physicochemical properties of soil such as texture, density, pH, solutes in soil, etc. important measurements and tests to determine soil dispersion potential such as pinhole, chemical, crumb and double hydrometry tests were performed based on ASTM standards. Finally, the validation of the tests was done based on the comparison of their results with each other.
Results and Discussion: The results show that the percentage of organic Carbon and soil porosity decreased from the surface (horizon A) to the depth of the soil (horizon B and C), while the apparent specific mass increased. Therefore, the change in soil properties from surface horizons to depth has caused a change in the degree of dispersion of these horizons. On the other hand, high amounts of exchangeable sodium in some horizons caused chemical dispersion, which indicates the role of sodium in increasing the thickness of the double layer of clay soil surfaces. However, the results of this research indicate that there is no severe dispersion of loess soils in Golestan province.On the other hand, the dispersion tests performed on these soils show that the dispersion phenomenon caused by the presence of sodium does not play a role in the erosion of these soils, and the dispersion of these soils is basically a physical phenomenon caused by the loess texture in the study area.
Conclusion: The results of the studies indicate that almost all the tests have the ability to detect the dispersion of the soil, the only difference is in expressing the intensity of the dispersion and actually the accuracy of the test. In determining the dispersion potential of soils, the pinhole test better models the actual state of water seepage in the cracks in the soil structure. So, in any case, the results of this test can represent the potential of real soil dispersion in the region. In determining the dispersion potential of soils, the Crumb test in loess soils showed the dispersion potential to be lower than the actual state, and the double hydrometric method had the most agreement with the results of the pinhole test.
Keywords: Loess soils, Dispersive soil, Pinhole test, Double hydrometric test.
کلیدواژه‌ها [English]
)