Distribution of total carbonate and iron oxides on catena at Duhok Governorate, Kurdistan Region, Iraq

The study area located at Zawita location, Duhok province, Kurdistan region, Iraq. Five pedons were digging on catena depending on the slope degree and slope aspects. Samples were air-dried, ground, and sieved using (2) mm sieve, in order to be used for physicochemical analysis. The soil texture varied from clay loam to sandy loam in the surface horizons of all pedons and became finer from the summit to foot slope in the south aspect, in contrast at the north aspect soil texture became coarser from the summit to foot slope). Study soils were less development and less differentiation of soil horizons in pedons at the summit and back slope in contrast to it at the foot slope of catena and were slightly alkaline nonsaline soils. Soil organic matter in the north aspect was more than it in the south aspect. CEC in all horizons for pedon (1) at the summit was high value when compared with it for pedons at the back slope and foot slope. Studied soils consider as calcareous that have a high content of carbonate minerals as a result of the calcification pedogenic process in turn these soils have a high buffering capacity. Total carbonate at the summit, was less amount, in the surface horizon (Ah) then was gradually increased in the subsurface horizon (Bc) after that uniformity increased of carbonate distribution in soil horizons (C1st) and (C2k), whereas was decreased in surface horizons at the back slope at both aspects but in north aspect was less than it at south aspect. In surface horizons, at foot slope in both directions, total carbonate was decreased, whereas the vertical distribution indicated increasing it towards deep horizons of pedons at foot slope. Iron oxides in soil samples were fluctuated between increase and decrease with the exception of pedon (4) at the back slope in the south aspect. Part of the iron oxides was translocation downslope with runoff water and adds it to iron oxides at the foot slope and a considerable amount of it was present in the study location that is causing the change in soil color. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study revealed significant variations in soil texture, organic matter content, and iron oxides distribution across different slopes and aspects. Soil development and horizon differentiation differed among pedons at different topographic positions. The translocation of iron oxides downslope and its accumulation at foot slopes play a role in changing soil color.