The Relationship between the Physico-Chemical Properties of Iranian Marl Soils and Soil Erosion Rate and Form.
Toraj Asadi, Islamic Azad University, Bandar Abbas Branch, PO Box.79145/1311 , Bandar Abbas, Iran., Bandar Abbas, Iran and Ali Reza Zahirnia, Soil and Watershed Managment Reaserch Institute, Tehran, Iran., Agriculture Faculty of Tehran University, Karaj, Iran, Terhan, Iran.
Marl soils are found in many part of Iran. The eroded soils in this arid region originate from sediments and occur in several colors such as gray, red and green. The erosion processes results in a lack of plant cover which decreases water permeability. Erosion, especially badlands erosion is one of the distinctive forces in marl regions and is one of the complex factors affecting marl erosion. Also, erosion depends on environmental factors like rain distribution and soil properties. The importance of marls is in type and amount of sediment that is produced and the variety of erosion forms. The effective longevity of huge dames in Iran such as Qom, Varamin, Semnan and Kerman have been decreasing. The study of erosion forms in marl soils demonstrated that there is a direct relationship between erosion forms and some soil physico-chemical. Of the erosion types (sheet erosion, rill erosion and badland) the most prominent on marl soils is rill and galley erosion. This is mainly due to high solution sodium and Sodium Absorption Ratio(SAR). When comparing of mean physico-chemical factors of marls with different erosion forms it was found that the amount of Na, Mg, SAR, pH and organic carbon have significant difference impacts on sheet, rill and badland erosion. The SAR value is the most important driving factor in marl soils and controls erosion indices. The occurrence of the causes of slop instability in marl soils formation and the lack of comprehensive research formed the main incentive to carry out the research presented in this paper. Key words: marl soils, badland, sheet and rill erosion, physico-chemical properties.