Soil is thin upper layer of the earth with unconsolidated materials where plant and animals derive their living. Soil catena refers to the sequence of different soils down a slope. the soil are usually derived from the same or similar parent materials but they vary with relief and drainage.
The following are main factors influencing the development of soil catena.
- Relief. This is the influence of topography on the surface soil. Slope influence drainage which in turn influence moisture content of the soil. Soil on the upper slopes are likely to be different from those of the valley floor. The upper slopes are generally steeper than the lower ones. They are therefore well drained. On the very steep slopes, the soils are thin because of high rate of erosion. On gentle slopes the soil is thick because the rates of erosion and weathering are balanced. On the valley floors the soils may be peat or alluvial due to deposition.
- Drainage. There is close relationship between drainage and slope. Soils are well drained on the steep slopes. Slope therefore affect the moisture content of the soil. The degree of slope and the amount of moisture are the major factors influencing soil changes along the slope. Generally, well drained mature soils are found at the hill top while thin, stony, dry and immature soils are found on the steep slopes. Grey soils which are formed through gleization process start to develop on damp, low alluvial slopes and finally give way to peat at a valley bottom where drainage is poor.
- Transport of soil debris. Surface run off and mass wasting are responsible for the downhill movements of sediments. This result in accumulation of deep soil called colluvial soil on the lower gentle slope. The steep slope are left thin, stony and immature soils with little organic matter and moisture. these soils are called xeromorphic soils.
- Leaching. where percolation of the soil solution tend to be horizontal soluble soil are removed from the soil of the upper slopes to the lower slopes. Other minerals, humus and clay may be transferred in suspension in the process of eluviation.
An ideal soil catena is best developed on the soil with uniform physical, chemical and textural characteristics as well as under uniform climatic condition.