Morphological, Pedological and Chemical Characterization and Classification of Soils in Morogoro District, Tanzania

Abstract

This study was carried out in Morogoro district, Tanzania to characterize and classify soils using USDA Soil Taxonomy and World Reference Base (WRB) for Soil classification methods. The site characteristics were identified during the reconnaissance survey for the determination of sampling units. Six soil profile pits namely TUG-P1, TUG-P2, TUG-P3, TUG-P4, TUG-P5, and TUG-P6 were excavated, described, and sampled for laboratory physico-chemical analysis. Topsoil bulky densities were determined and ranged from 1.23 to 1.37 g cm⁻³. The surface soil pH ranged from moderately acidic to slightly acidic (5.69–6.58) and subsoil from strongly acidic to neutral (4.72–7.30). Soil organic carbon (OC) was low for both top (2.93–4.79 g kg⁻¹) and subsoil (2.34–3.51 g kg⁻¹). Total nitrogen was medium (2–4 g kg⁻¹ for the topsoil and 2–3 g kg⁻¹ for the subsoil. Available P rated low with the top soil having 4.81–6.22 cmol kg⁻¹ and subsoil recording 3.12–6.14 cmol kg⁻¹. The cation exchange capacity for topsoil ranged from 5.31 to 8.10 cmol kg⁻¹ whereas for subsoil it was 4.91–8.10 cmol kg⁻¹. Using the USDA Soil Taxonomy, soils were classified as Rhodic Siderudox (TUG- P1), Typic Sombrustert (TUG- P2), Typic Eutrustolls (TUG- P3), Psamm Haplustepts (TUG- P4), Typic siderustepts (TUG- P5) and Typic Siderudox (TUG- P6). Under WRB, soil was classified as Rhodic Umbric Ferralsols (Eutric, Arenic) (TUG- P1), Haplic Vertsols (Aric, Orchric) (TUG- P2), Rhodic Eutric Cambisols (Arenic, Aric) (TUG- P3), Haplic Arenosols (Aric, Orchric) (TUG- P4), Rhodic Umbric Ferralsols (Eutric, Arenic) (TUG- P5) and Umbric Ferralsols (Eutric, Arenic) (TUG- P6). Soils showed a high level of weathering of parent material with deep depth, and fine texture dominated by sesquioxides and kaolinitic clays. To sustain yields, the soil’s nutrient management ought to involve the use of integrated approaches such as the application of inorganic (synthetic fertilizer) and organic nutrient inputs.