Spatial and Temporal Variations of Some Soil Properties at Northeast Nuba Mountains, South Kordofan State, Sudan

The sources of soil variability in the study area in the Northeast Nuba Mountains were examined for a better understanding of complex relations between soil properties, environmental factors and land use systems. The regional level as affected by soil-forming factors and the local level as affected by land use were considered. Soil samples collected throughout a 2500 km2area. Analysis of Variance (ANOVA), Principal Component Analysis, cluster analysis and Variogram Modeling were applied. Soil properties exhibit a spatial dependence with regional trend. Cluster analysis, and soil classification (Pacheco and Dawoud, 1976) showed that the soils of the study area can be grouped into two main classes (Vertisols and Alfisols). Soil ECand Clay content were the best explained by regional factors of soil variation. Two levels of soil information were studied, (i) the regional level of soil spatial distribution as affected by regional trend, using elevation as a proxy for soil-forming factors and (ii) the local level of soils variation as affected by land cover. Two fixed soil layers (0-20 cm, and 20-40 cm) were used for all the analyses. Geographic analyses and visualizations were performed with GIS and the Geomantic software. Regional and local effects and their interaction accounted for 70 % (based on clay) to 85 % (based on pH) of the total variance. The study revealed that research on appropriate management practices for resource use should focus chiefly on processes and factors occurring at the local level, as shown by the great influence of the dynamical land use system.