Browsing by Author "Bosiako, Ohene Antwi"

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    Using Caecium-137, Lead-210 and particle size fractions to model spatial soil erosion rates in the forest-savannah transition ecology of the Volta Basin of Ghana
    (2006) Bosiako, Ohene Antwi
    Sustainable land management practices are limited by immediate access to long-term spatial data on erosion rates by all processes. Compared to the current erosion assessment methods of erosion plots, survey of erosion features and modelling, the erosion tracer technique has been found to overcome the above limitations. The objectives of the study were to assess the long-term soil erosion rates under different land uses by using 137Cs, 210pb and particle size fractions (PSFs) as tracers, evaluate the performance of some of the existing calibration models, establish the relationships between the different tracers to facilitate the generation of uniform values irrespective of the tracer used and finally, and to determine the spatial distribution of the tracer-derived erosion rates and their implications on some parameters of topsoil quality. The study was at GLOWA-Volta experimental site on longitude 001° 16’ W and latitude 07° 19 - 20’ N within the Volta Basin of Ghana. Soil and land-use data were collected along grid points for spatial analysis. The data included caesium-137, lead-210, infiltration rate, hydraulic conductivity, particle size distribution, organic carbon, exchangeable potassium, available phosphorus and rainfall. The calibration models were the Proportional (CsPM), Mass Balance 1 (CsMB1), Mass balance 2 (CsMB2) and Diffusion and Migration (CsDM) models for 137Cs, Mass Balance (PbMB) and Diffusion and Migration (PbDM) models for 210Pb, clay ratio (CR), sand ratio (SR) and NUSLE (soil erodibility from the Universal Soil Loss Equation (USLE) nomograph) for particle size fractions. The study determined the reference values of the tracers: 668 ± 90 Bq m-2 and 12680 ± 1700 for 137Cs and 210Pb, respectively, SR was 0.99 ± 0.13, CR (4.85 ± 1.89) and NUSLE (0.58 ± 0.07). CsPM, CsMB1 and NUSLE predicted very low erosion rates typical of fallow lands (S 1.0 Mg ha-1yr-1); PbDM, SR, and CR for moderate erosion rates from a land rotation system ( 5.0 Mg ha-1y-1) and CsMB2 and PbMB for high erosion rates from intensively cultivated fields (: 5.0 Mg h-1y-1). Variance reduction tools and Morgan’s ratio were used to determine the performance of the models. The study established that the risk associated with predicting erosion rates was in the order: CsPM (CV=85 %)