CRYSTALLINE AND AMORPHOUS FORMS OF IRON (Fe) OXIDES IN HYDROMORPHIC SOILS OF DADIN KOWA, GOMBE STATE, NIGERIA

Abstract

The content and distribution of different forms of Iron oxides are important indicators used in describing soils. This study was conducted with the aim of evaluating the crystalline and the amorphous forms of Iron oxides distribution in hydromorphic soils across five different land uses (amaranth, millet, mango, rice and tomato) at Dadin Kowa, Gombe State. Two soil profile pits were dug in each of the identified land uses, and soil samples collected from identified genetic horizons. All soil samples collected were analyzed using standard laboratory procedures. The textural classes of the soils revealed loamy sand to sandy loam. Bulk density, particle density, total porosity and silt/clay ratio varied between 1.60 to1.67 g/cm³, 2.57 to 2.71 g/cm³, 35.82 to 40.41% and 0.92 to 1.86, respectively. The soil reaction was slightly acidic to neutral (pH 6.39 – 6.68). Soil electrical conductivity (EC) for all the soil mapping units was below the critical limits of 4 d/Sm EC, an indication of the non-saline nature of the studied soils. The values for OC, TN and AP contents of the soils across land use and horizons was substantial > 10 g/kg, and is rated medium to high, 1.1 to 1.40 g/kg, rated low to medium and 8.03 to 9.35 mg/kg, rated low, respectively, while the exchangeable bases were generally rated medium to high. The mean distribution of forms of Fe oxides, extracted by different extracting reagents revealed the dominance of diotonite extractable iron (Fed) over oxalate extractable iron (Feox) and pyrophosphate extractable iron (Fep), while the active iron ratios was generally <0.4 but > 0.1, confirming a moderate stage of soil development, and the dominance of crystalline forms of Fe oxide as against the amorphous forms across the study area. The direction of soil development with age followed the trend; amaranth < mango < millet < tomato <rice.