عنوان مقاله [English]
Genesis, classification and morphological and physico-chemical characteristics of Rajain’s plain soils affected by topography, as a soil forming factor, under semiarid condition of East Azarbayejan province in northwest of Iran with calcareous parent materials were studied. This plain with 42000 ha. is located in 35 th km southeast of Miyaneh in East Azarbayejan province. The soils of the studied area have “Xeric” moisture regime and “Mesic” temperature regime. The average plain elevation is 1290 m above sea level. The mean annual precipitation and temperature are 305.4 mm and 12.9ºC, respectively. Three physiographic units including plateaus, piedmont alluvial plains and river alluvial plains were identified. According to results of field observation and laboratory analysis, it seems that topography and time are the main factors affecting soil formation at the studied area. They caused differences among the soil characteristics in this area. Topographical variation from upper plateaus to lands of riversides and also rate of runoff, amount of water penetration into soil and vertical translocation of salts and materials within the soil profile have affected soil development and genesis. Entisols are observed in river alluvial plains and southern piedmont alluvial plains without distribution of secondary calcium carbonate and any development of profile and only with ochric epipedon. Inceptisols showed B horizon, calcic horizon and cambic horizon which are characteristic of an early stage of soil development.