Soil, Water and Nutrients
Brian Huntley
Abstract
Abstract This Chapter provides an introduction to basic elements of soil science, from an understanding of the soil profile, its develop and its importance to plant growth. The processes of weathering and the development of laterites, calcretes, salinised and other major soil types and their distribution in Angola are described. Soil water relations and soil chemistry and thus the availability of water and nutrients are fundamental determinants of plant growth, species composition and productivity. The differences between dystrophic (low base status) and eutrophic (high base status) soils and the distribution of the mesic/dystrophic savanna biome and the arid/eutrophic savanna biome, which dominate Angolan landscapes (totaling over 90% of the vegetation mantle of the country) are emphasised. The Key Soil Groups of Angola are mapped and their characteristics summarised. Sandy arenosols cover 53% of Angola, mainly comprising the Kalahari sands of the eastern half of Angola. Ferralsols cover 23% of Angola, occupying the spine of crystalline rocks along the western highlands. Both are of low nutrient status but carry dense miombo woodlands where they have not been transformed by human activities. Richer soils occur along the escarpment and hot coastal lowlands. The processes of land degradation, due to inappropriate soil management threaten the livelihoods of communities living on these fragile soils, are described.