The Nature of Iron Oxide Distribution in Some Calcareous and Gypsiferous Soils

The study area is located within two regions. The first site in Tikrit city (Tikrit University) represents gypsiferous soils and the second site represents calcareous soils in Erbil Governorate. Two pedons were chosen in Tikrit P1 (rainfed) and P2 (cultivated), and two other pedons in Erbil P3 (rainfed) and P4 ( cultivated) . Tikrit pedons showed presence of gypsum crystals of spindle and lenticular type with a length ranging between (0.2 -0.5) mm , the pores type of vughs and chamber, while the dominance of the planer and interconnected chamber pores in Erbil pedons. Iron oxides appeared in different forms of single discrete particles or Ferriargillans cutan especially in Erbil's pedons, The values ​​of iron oxides varied, as the dominance of the total, free ,and the amorphous iron oxides in Erbil pedons were ranged between (8.77 -12.81), (8.17 - 10.30), (6.82 - 9.19) g.kg-1, respectively, compared with the iron oxides themselves for Tikrit pedons, which ranged between (2.98 - 5.39), (2.45 - 4.86), (1.19 - 2.67) g.kg-1, respectively. While the amorphous iron oxide values ​​showed an  increasing in the Tikrit pedons compared with  Erbil pedons, as their values ​​in Tikrit ranged between (1.26 - 2.19) g. kg -1 while in Erbil pedons ranged between (1.01 – 1.81) g. kg -1.