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Key points
- Soils in Namibia are largely a product of its arid and semi-arid environment, as seen in the origins and properties of the five soil groups that cover most (94 per cent) of the country. The first three of the following soils are sedimentary in origin, having been deposited by wind or water. They are found largely in the eastern and central regions of Namibia.
- Arensols (covering 35.4 per cent of Namibia) are deep sandy soils recently deposited as dunes, sandy plains and beaches, and sands formed by the local weathering of quartz-rich sediments or rocks such as sandstone, granite and quartzite. They hold little water or nutrients. They form the dunes on the coastal plain and cover much of eastern and northeastern Namibia.
- Calcisols (14.2 per cent) are also formed from sediments, but from those that are rich in calcium and magnesium and that accumulate in arid and semi-arid environments.
- Cambisols (9.2 per cent) form from parent materials rich in calcium. They are typical of arid and semi-arid environments with distinct dry seasons and high rates of evaporation.
- Leptosols (23.4 per cent) are shallow, stony soils that form locally from the weathering of rocks. Regosols (12.5 per cent) also form locally. They are young, minimally developed and highly erodible soils with no distinct horizons. They are common in young sediments, particularly in arid and semi-arid areas.
- Gypsisols, Solonetzes and Solonchaks are found along the coast and/or in pans where they develop from concentrations of calcium sulphates, sodium salts and a variety of other salts, respectively.
- Soil qualities are determined by a variety of properties. Those mapped here are soil depth, density, waterholding capacity, organic carbon content, cation exchange capacity, pH and texture.
- With few exceptions Namibian soils support limited plant growth, largely because of the arid environment. This limits the volume of plant litter which can be turned into organic matter in the soil, thus restricting fertility and microbial life. Low rainfall also slows the chemical weathering of rocks and thus the supply of nutrients to plants, and soils are often shallow as a result of slow weathering. High rates of evaporation can create an accumulation of toxic salts in the soil. Arid conditions have led to the deposition of windblown sand of inert quartz crystals which cover more than a third of Namibia, and hold little water within reach of plant roots.
- Other constraints arise from the capping and compaction of silty and fine, sandy soils. The accumulation of silica and salts may harden soils which then causes poor infiltration and waterlogging. Organic matter also mineralises rapidly in soils heated excessively by direct sun.
- Namibian agriculture is severely limited by its soils which constrain both crop production and the growth of livestock forage. Measures can be employed to improve soil fertility, but they are too expensive for most farmers, especially if the returns on investment are variable or modest.
- The overall quality of Namibia's soil is one of three major reasons for the country's small human population and low biomass of plants and animals. The others are high evaporation and low rainfall.
