Soil functioning and interrelations with hydrophysical attributes and organic and microstructural fractions in soils under land uses in the Brazilian Semiarid.

Abstract

Soil functioning in drylands is shaped by interrelations among physical attributes, micromorphological properties, and chemical organic matter fractions. In this scenario, this study aimed to evaluate how these interrelations influence soil functioning, incorporating micromorphology, across different land uses in the Brazilian semiarid region. The research was conducted in the rural community Piracicaba, Upanema, RN, Brazil, across six land uses: banana (Cambisol), papaya (Cambisol), Barbados cherry (Cambisol), fallow land (Cambisol), native pasture (Acrisol), and native forest (Ferralsol). Disturbed and undisturbed soil samples were collected from 0.00-0.05 m, 0.05-0.10 m, 0.10-0.15 m, and 0.15-0.30 m depths for hydrophysical and chemical analyses. Micromorphology (0.00-0.05 m) was examined using scanning electron microscopy (SEM) with deformed samples. Multivariate statistics were used as the main tool through the correlation matrix, factor analysis (FA) and principal component analysis (PCA). Factor analysis identified three key factors: F1: Bulk density (Bd), Weight mean diameter (WMD), phosphorus (P), total organic carbon (TOC), humin (C-HUM), humic acid (C-HA), labile carbon (LC), and carbon management index (CMI). F2 (microporosity, field capacity (FC), relative hydraulic conductivity (Kr), aeration porosity (Ap), Calcium (Ca²⁺), and cation exchange capacity (CEC), and F3 (silt and available water (AW). Principal component analysis (PCA) differentiated variables and land uses. Papaya and native forest were associated with TOC, C-HUM, C-HA, C-FA, and phosphorus, indicating superior structural and organic functionality. In contrast, microporosity, field capacity, permanent wilting point (PWP), and clay characterized Barbados cherry and fallow soils. Silt, AW, WMD, exchangeable bases, CEC, and base saturation (V%) distinguished Cambisol land uses, while macroporosity, sand, and Kr differentiated pastures. Bulk density (BD) highlighted contrasts between native forest and pasture. SEM photomicrographs revealed organo-mineral interactions in banana, papaya, and Barbados cherry soils. Fallow soils showed compact particles and compromising functionality. Pasture soils exhibited limited organo-mineral interaction, and smaller roots. Conversely, we can infer native forest soils displayed roots, fungal hyphae, and bacterial cell fragments, reflecting a complex system linked to environmental stability. The findings conclude that maintaining organic residues and litter on the soil surface enhances structural functionality in banana, papaya, Barbados cherry, and native forest soils, as evidenced by hydrophysical attributes and organic fractions. Micromorphology effectively differentiated particle size, shape, roughness, structures across land uses.