Total Iron and Different Iron Forms Contents Affecting by Soil Characteristics in Vertisols, SE Turkey

Iron (Fe) in the soil is a very important element for agricultural applications and the development of plants, which have different forms. The presence of Fe in the rhizosphere is controlled by the activity of Fe forms in the soil and the microorganisms and surrounding root-soil interaction of plants and roots. The objectives of this study were to identify, and to examine their interaction with soil properties in vertisols. The results showed that; FeT contents ranged from 1.17 and 47.71 g kg-1, mean 13.81 g kg-1 › FeD contents 0.18 to 17.85 g kg-1 and mean 7.23 g kg-1 › FeO contents 0.01–0.31 g kg-1 mean 0.18 g kg-1 › FeDTPA contents 0.00–0.17 g kg-1 mean 0.04 g kg-1 › FeP contents 0.00–0.02 g kg-1 mean 0.01 g kg-1. Clay-silt fractions and organic matter had a very powerful impression on Fe forms distribution. FeD, FeDTPA, FeO ve FeP had low quantities. This is thought to be due to insufficient rainfall and some soil characteristics (including high pH, low organic matter, clay texture, and high lime content), as iron is not easily dissolved in the soil. There was a very important relation between clay content, organic matter, silt fractions, and Fe forms in the studied area. There was a positive correlation between soil organic carbon and DTPA-extractable Fe. There was a negative correlation between DTPA-extractable Fe and soil pH, also calcium carbonate content. When total Fe was rised, clay-silt content and cation exchange capacity (CEC) increased in the soil profiles. Especially in Zone 3 has more Fe and Fe contents, the results showed that; There was a very good balance between the different Fe fractions and soil properties. Zone 3 had more total iron contents than the other zones, because of their soil properties. Fe bound by organic sites, water-soluble plus exchangeable Fe and Fe were adsorbed onto oxides (amorphous surfaces) and were positively correlated with the DTPA-extractable Fe.