Factors influencing soil distribution and their implication for agricultural land management in Morogoro urban District, Tanzania

Abstract

A standard soil and land resources survey was conducted in Morogoro Urban District, Tanzania to investigate the factors influencing characteristics and spatial distribution of soils and their implication for land management. Landforms, parent materials, climate, soil morphological, physicochemical and mineralogical properties were the main attributes studied. Soils were classified according to the FAO-World Reference Basefor Soil Resources. Six major landforms were identified namely; strongly dissected mountain ridges, mountain foothills, hills, piedmonts, peneplains and valleys. The strongly dissected mountain ridges comprise complex soils developed on pyroxene granulites. The soils include shallow, excessively drained sandy clay loams and deep well drained sandy clays and clays. The soils were classified as Lithic-Paralithic Leptosols, Hapli-Profondic Lixisols, Orthidystri-Episkeletic Cambisols and Hypereutri-Episkeletic Cambisols (Haplic). The hills are a complex of rock outcrops and shallow soils developed on muscovite-biotite migmatites. The soils are excessively drained, extremely gravely sandy loams and sandy clay loams. The soils were classified as Lithic Leptosols. The piedmonts and peneplains comprise largely associations of deep and very deep, well drained clays and sandy clays. These soils developed on colluvium derived from granulites and migmatites were classified as Chromi-Profondic Acrisols, Chromi-Profondic Lixisols, Rhodi-Profondic Luvisols and Cutani-Profondic Luvisols (Haplic). In the valleys, the soils are developed on alluvium of diverse mineralogical composition and are a complex of Calcari- and Stagni-Mollic Fluvisols and Calcari-Salic Vertisols. All the studied soils except those of the valleys have low soil fertility as shown by low organic carbon «1.0%), low levels of major nutrients (nitrogen <0.1%, phosphorus <5 mg/kg) and low CEC «12.0 cmol(+)lkg soil). Although the soils of the valleys are fertile, they are characterised by one or more of the following problems: poor drainage condition, high alkalinity and salinity (ESP >5%) and difficult workability. The results of this study show a close relationship between landforms, parent materials and soil types. The paper establishes some land qualities which are important for sustainable agricultural land management in the district.