Discriminant pedological factors of in situ specific moisture and available water content of African soils

The management of groundwater and crop-available water requires the knowledge of the hydrological behaviour of soils. A study was carried out from North to South Senegal on about 5 degrees of latitude, which cover a large range of pedological factors and various climatic, geologic and geomorphologic conditions. 1387 layer samples of 103 soils were taken from the surface to 2 m depth by 0.1 m-deep increments. The studied pedological properties were clay + silt content, bulk density, exchangeable Na + and pH. The hydraulic properties were the minimum moisture content, the field capacity and the available water content. Principal component analysis shows that the main factors, the texture, the minimum moisture content and field capacity, the available water content and the pH were in a decreasing order of importance. A good agreement between predicted and measured values of the minimum moisture content and the field capacity data, except for the available water content, was found for all mixed layers, for soils grouped according to their layers and for two soils (Arenosol and Ferralsol). However, the available water content can be calculated by statistical calculation by the grouping of textural classes for each layer.