Work

Influence of parent material on mineralogy and iron forms in semiarid soils

Year: 2026

Type: article

Abstract: ABSTRACT Soil mineralogy is a major determinant of soil physical, chemical, and biological properties. In semiarid environments, pronounced mineralogical heterogeneity requires specific management practices. This study characterized the mineralogy of the clay fraction of soils from rural communities in Mossoró, Rio Grande do Norte, Brazil, and evaluated the influence of parent material on mineralogical composition and pedogenetic development. Eight soil profiles were selected from 15 previously described profiles, and mineralogical analyses were performed on their diagnostic horizons. Iron forms were quantified by sulfuric acid digestion to determine iron associated with secondary minerals (Fes), dithionite-citrate-bicarbonate extraction to quantify free crystalline iron (Fed), and acid ammonium oxalate extraction to estimate low-crystallinity iron (Feo). The qualitative mineralogy of the clay fraction was determined by X-ray diffraction (XRD) using oriented slides subjected to the different chemical and thermal treatments. The soils were classified predominantly as mesoferric and hypoferric. XRD indicated the predominance of kaolinite, 2:1 phyllosilicates, probably illite and/or smectite, and iron oxides, with limited variation among parent materials. Under semiarid conditions, weathering and pedogenetic evolution, expressed by the mineral assemblage of the clay fraction and by iron forms, directly depended on parent material. These characteristics influence nutrient dynamics, natural soil fertility, and agricultural management in semiarid regions.

Source: Revista Caatinga

DOI: 10.1590/1983-21252026v3914241rc