. Iron oxides in the soil consisted of goethite (α-FeOOH) with yellow or brown colour, hemathite (α-Fe2O3) with red, lepidocrocite (γ-FeOOH) with yellow, maghemite (γ-Fe2O3), magnetite (Fe3O4) with black and feryhidrite (5Fe2O3.9H2O or Fe5HO8.4H2O) have different levels of reactivity against different ions in the soil which is influenced by positive and negative charge of the surface of the iron oxide. Acid sulphate soil is one of the soils in wetlands that contain higher sulfidic materials (pyrite). Pyrite oxidation in acid sulphate soil is not only increasing acidity but also producing iron (III) colloidal, which over time will form the iron oxide goethite. The presence of organic ligands in soils has an important role to the crystallization of iron oxides in the soil. The greater the ratio of ligand/Fe (II) in the soil greatly inhibited the crystallization of iron oxide. The presence of citrate ligands in acid soils affects the surface properties of Fe oxides. The presence of organic acid as an organic ligand will affect the formation of goethite and hemathite from ferryhidrite.