Forms of iron in soils on basement complex rocks of Kaduna state in northern guinea Savanna of Nigeria

Abstract

The forms of iron extracted by different methods were studied in soils developed on four basement complex rocks within Northern Guinea Savanna of Nigeria namely: migmatite gneisses, older granite, quartzites and mica schists. The study shows that forms of iron generally decreased in the order of total elemental iron (Fe T) determined by XRF > double acid extractable total iron (Fe a) > dithionite extractable iron oxide (Fe d) > oxalate extractable iron oxide (Fe x) > pyrophosphate extractable iron oxide (Fe p) > 0.1M HCl extractable micronutrient available iron (Fe h). Variation in content of total irons (Fe T and Fe a) were not significant in the soils, but content of Fe h , Fe d , Fe x and Fe x/d significantly varied in the soils on the various parent materials. Therefore processes and extent of pedogenesis were considered to influence the variations resulting in recrystallization and increase in content of Fe h and Fe d in these soils. The significant correlation between various forms of Fe (Fe a , Fe d , and Fe x) with active iron ratio further affirmed that as soils on basement complexes increase in their pedogenetic age, Fe content generally increases irrespective of total forms of iron. The strong correlation between Fe T , Fe a and Fe d indicate that these forms of iron were extracted from similar sources.

Impact of Texture on Sesquioxide Distribution in Southeastern Nigerian Soils

“…Several physiochemical properties especially sand, silt, clay, silt/clay ratio, TN, OM, P, Ca, K, Mg, Na, H, ECEC and % BS have been reported to affect sesquioxide contents of soils (Uzoho, 2014). Maniyunda et al (2015) obtained strong relationships between sesquioxides with clay and soil organic matter contents while Osodeke et al (2005) noted positive relationships between DCB-Al with clay and sand and oxalate Fe with clay and organic matter contents of soils along a toposequence in Umudike area of southeastern, Nigeria,.…”

“…Sesquioxides are oxides, hydroxides and oxy-hydroxides of Al, Fe, Mn, Si and Ti that are present as coatings or discrete particles on the soil surfaces (Uzoho, 2014;Maniyunda et al, 2015). They are crystalline or amorphous in nature, even though a small fraction exists as organic complex and together they influence soil physiochemical properties (Osodeke et al, 2005).…”

“…It has been indicated that dithionite extractable Fe and Al constitutes a reasonable estimate of total pedogenic free Fe and Al oxides while oxalate extractable is for the amorphous Fe and Al oxides (Hassan et al, 2005). Crystalline (free) or dithionate extractable iron oxides represent total pedogenic iron that are present as geothites, lepidocricite and haematite while aluminium occurs as gibbsite in soils (Osodeke et al, 2005;Maniyunda et al, 2015). It has also been noted that extractable dithionite-citrate manganese and silicon constitutes easily reducible manganese and silicon forms in soils respectively (NSSC, 1995).…”

“…Distribution of sesquioxides varies with landscape positions. For instance, variation with landscape positions have been reported in soils of inland valleys (Essoka and Esu, 2000), contrasting land units (Uzoho, 2014), toposequences (Osodeke et al, 2005;Enya et al, 2011), granitic and basement complex rocks (Hassan et al, 2005;Maniyunda et al, 2015;Olatunji et al, 2015) and soil profile depths (Essoka and Esu, 2000). According to Wei et al (2010), landscape influence could be associated with the topography, drainage condition, parent materials and land use types and affects soil chemical properties and water movement conditions.…”

“…Though sesquioxide concentrations of most Nigerian, soils have been studied (Osodeke et al, 2005;Hassan et al, 2005;Enya et al, 2010;Uzoho,2014;Maniyunda et al, 2015), there appears to be a dearth of information on their distribution in soil particle size fractions. The objectives of this study were therefore to evaluate the impact of texture on sesquioxide contents of soils of contrasting landscapes in a humid tropical rainforest, relationship between bulk soil and particle size sesquioxide concentrations and correlation between sesquioxide contents and selected physicochemical properties of the bulk soil.…”