Browsing by Author "Mbogoni, J. D. J."

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Assessing drivers of soil properties and classification in the West Usambara mountains, Tanzania
(Elsevier, 2017-10-16) Massawe, B. H. J.; Winowiecki, L.; Meliyo, J. L.; Mbogoni, J. D. J.; Msanya, B. M.; Kimaro, D.; Deckersf, J.; Gulinck, H.; Lyamchai, C.; Sayula, G.; Msokah, E.; Vagen, T.; Brush, G.; Jelinskii, N. A.
Improved soil information in tropical montane regions is critical for conservation, sustainable agricultural management, and land use planning, but is often challenged by topographic and land-use heterogeneity. The West Usambara mountains are a part of the Eastern Arc chain of mountains of Tanzania and Kenya, a globally important tropical montane ecoregion made up of isolated fault-block mountain complexes characterized by high biological endemism, population density, and agronomic productivity. We synthesized novel and legacy soil data from published and unpublished studies to better understand the drivers of soil property distributions and soil diversity in the West Usambaras, and to serve as a foundation for improved soil mapping efforts across the Eastern Arc. Analysis of the resulting dataset of 468 sites (ranging in elevation from 1040 to 2230 m.a.s.l.) revealed that soil properties varied more significantly by land use and topography than by soil type, suggesting that future mapping efforts in the region should focus primarily on soil property prediction and secondarily on soil classification. Sites under cultivated land uses had the lowest topsoil soil organic carbon (SOC) concentrations and highest pH values, and SOC generally increased with increasing elevation. Valley soils had significantly lower surface SOC concentrations but higher exchangeable bases and pH values than all other landscape positions. Soil pH decreased by an average of 3.5 units across the entire elevation gradient and decreased by 1 unit with elevation even after SOC, land use and landscape position were included in multiple regression models. The relationship of cation exchange capacity (CEC) to SOC and clay content varied by landscape position. Therefore, particularly in montane regions where soils can vary significantly over short distances, multiple functions may be necessary to produce improved estimates of parameters such as CEC. Soil classification was driven most strongly by topography, with Acrisols (WRB Reference Group) and Ultisols (U.S. Soil Taxonomy (ST)) as the dominant soil types, located primarily on mid slope, upper slope and crest landscape positions, making up 47% and 75% of observed profiles, respectively. However, five ST Orders and seven WRB Reference Groups were present in the dataset, with the highest soil diversity occurring at lower slope landscape positions. Conclusions drawn from this large dataset support previous work in the West Usambaras and provide a conceptual foundation from which to build improved soil maps across the Eastern Arc and in other tropical montane systems throughout the world.
Factors influencing soil distribution and their implication for agricultural land management in Morogoro urban District, Tanzania
(2000-04) Msanya, B. M.; Mbogoni, J. D. J.; Kimaro, D. N.; kimbi, G. G.; Kilasara, M.; Deckers, J.S.
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.