Determining of The Most Important Factors in Infiltration Rates of the Soils formed on Gachsaran and Aghajari formations in Various Land Uses

Infiltration is the most important process in soil hydrology. As the early Miocene Gachsaran Formation (GF), and the late Miocene to Pliocene Aghajari Formation (AJF) cover a substantial area in western and southwestern Iran, it is very desirable to investigate the effective factors that determine their infiltrability, particularly in different land uses. Therefore, two sub water-sheds of the Margha (AJF, 1609 ha) and the Gach Mountain (GF, 1202) in the vicinity of the City of Izeh, were selected. Infiltration rate (IR) was measured in seven plots on the AJF and in six plots on the GF, both with three replication (rangeland, farm field, residential areas). A comforts’ (?) rainfall simulator, which delivered the intensities of 0.75, 1.00 and 1.25 mm per minute was used on both formation. The 0-20 cm of soil was sampled at each plot on which the IR had been determined. Percentage of the very fine sand, sand, clay, silt, pH, EC, soil moisture, %CaCo3 and %OM were determined using common laboratory procedures.A multivariate regression was performed to identify the characteristics which affect the determined IR. It was observed that silt, very fine sand, EC, pH, %OM and %CaCo3 demonstrated the most important roles in the runoff production. However, the CaCo3 content of each formation had the highest positive role in the IR.