Explain the factors which influence soil profile development in East Africa.

Candidates are expected to explain the conditions for soil profile development

Nature of the parent Rock

• Hard rocks which are not easily weathered such as granite lead to formation of thin soils and poorly developed profiles while soft rocks which are easily weathered such as volcanic ash and limestone lead to the development of a deep soil
• Rocks with joints and cracks are also easily broken down to produce deep/mature soil profiles as compared to those without
• Dark coloured rocks responsive to heat are also easily weathered to produce deep /well developed profiles as compared to light coloured rocks which are difficult to break
• Basic igneous rocks which are difficult to weather as well as some sedimentary rocks (composed of previously weathered materials are difficult to breakdown and produce shallow soils in immature/ poorly developed soil

• Permeable/ porous rocks are easily weathered by chemical processes to produce deep mature soil profile as compared to impermeable rocks which may produce shallow soil profiles

Climate

• It determines the character and rate of In hot humid climates, chemical weathering occurs at a fast rate leading to the formation of deep soils and well developed/ mature soil profiles.
• In hot dry climates physical weathering predominates leading to the formation of thin/ skeletal soils/ azonal soils which do not have well developed profiles.

Vegetation.

• Thick vegetation cover decays and leads to the formation of humus which is added to horizon A of the soil profile
• Plant roots also lead to the disintegration of rocks and the formation of soil in a soil
• Forested areas such as Mabira, kakamaga, Kissi in Kenya therefore tend to have deep soils in well- developed profiles while areas with thin vegetation cover have thin skeletal soils and poorly developed profiles.

Drainage

• Water logged conditions do not allow the easy development of a soil profile such as Lutembe wetlands, Katonga, Awoja wetlands,
• Well drained areas lead to the formation of a well-developed mature soil profile such as areas around L. Victoria

• Human activities

– Such as mining, quarrying, road construction etc. lead to the breakdown of rocks and the formation of deep soils characteristic of well-developed profiles e.g. mining in Tororo, cultivation around L. Victoria.

Living organisms

– In the soil such as ants, earthworms and mammals like rats and moles also break down rocks as the construct their passages underground leading to the formation of deep soils and well developed soil profiles

Time

– Ample time is required to the formation of mature, fertile and deep soils in a well-developed soil profile.

If time is short  immature/ azonal soils will formed with poorly developed /shallow soil profiles.

Topography.

• Steep-s lopes are- more susceptible to soil erosion, and thin soil profile
• Gentle slopes – erosion is slower, there is a lot of deposition of soil eroded on steep slopes and min water percolates to assist in soil profile development leading to deep, mature soil profile.
• Valleys; lowlands; extensive deposition and percolation of water lead to deep mature soil profiles where there arc waterlogged conditions there is immature soil