Soils of the Shahrazur Area (NE Iraq): II—Genesis and Classification

Five typical pedons developed on limestone, alluvium and/or colluvium, under semi-arid thermic climatic and steppic grass vegetation and representing varying topographic positions were investigated for evaluating the rote of different soil forming factors in the genetic evolution of the soils. The process of melanization appears to be active. Leaching is not effective in decalcifying these heavy-textured soils due to steep hill slopes, slow intake rates, light winter rains and shrink-swell characteristic (especially in the intermontane valley plains). The soils in the hilly areas show A-B profiles, while those of the intermontane valley plains show A—C profiles. The horizonation, especially in the intermontane valley plains, appears to be prevented by the churning process. A good relationship exists between different soil forming factors and soil development. While climate and vegetation appear to be the dominant factors responsible for the development of Mollisols in the hilly areas, the parent material and topography contribute to the development of Vertisols in the intermontane valley plains. The soils have been classified as Haploxerolls, Calclxerolls, Haplaquolls and Chromexererts. The Mollisols, occupying 54 per cent of the area, are predominant in the hills whereas the Vertisols, occupying 31 per cent of the mapped area, are confined to the plains.