Ethnopedological knowledge and scientific assessment of earthenware pottery-making soils of southern Botswana for natural resource management

Abstract

Earthenware pottery making, a major occupation among rural dwellers in southern Botswana, has been one of the mainstay of their economy for centuries. Consequently, local potters have classified their pottery-making soils based on indigenous knowledge with no verifiable scientific support. This study explores information on the criteria used by indigenous potters in classifying pottery-making soils in southern Botswana. It also presents results on pedological parameters of the soils. Routine laboratory procedures were used to measure properties of two representative pedons. Three properties, namely colour, texture (clayeyness) and plasticity are the major factors used in classifying pottery-making soils in Botswana. Two soils were identified: seloko se se hibidu (red clay) and seloko se se sweu (white clay) as the soils used for pottery. With the exception of texture, data on scientific analysis are consistent with indigenous soil classification system. The soils had sandy clay loam texture with clay contents ranging from 25.3 to 31.8 %, while sand dominates with over 50 % composition in the two pedons. The soils have mixed clay mineralogical assemblage consisting of sepiolite, smectite, kaolinite, illite, mica and montmorillonite and vermiculite. The coefficient of linear extensibility (COLErod) of the soils are high to very high (0.10 – 0.18), implying the dorminance of 2:1 clay minerals. As the depth increased, the soil colour became more reddish (LT1; 10YR 5/3 > 10R 7/3 and LT2: 10YR 8/2 > 10R 8/2 > 10R 7/4 > 10R 7/4). Overall, the geochemical molecular ratios points to slow pedogenic processes including hydrolysis, leaching, salinization and calcification in the soils. Data on the pedological properties of the pottery-making soils would find enormous application in sustainable management of the soil resources.