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In this lesson 3we are going to discuss about azonal, intrazonal and zonal soils

Answer Text:
Soil Classification
- Grouping of soil according to specific properties such as age, texture, colour and climate.
1. Zonal Order
Mature soils with a well developed profile due to having undergone long time soil formation processes under good drainage conditions.
Sub-orders
a) Podsols
- Infertile and acidic soils which are heavily leached with base compounds like calcium removed leaving aluminium and iron compounds
- Found in forested areas and higher latitudes e.g. Scandinavian countries and Canadian Shield.
b) Podzolic Soils
- Soils similar with Podsols but found in areas with deciduous forests and hot climates e.g. Congo Basin and Kenya highlands.
c) Tundra Soils
- Soils with excessive moisture due to low evaporation rate causing permanent freezing of the soil.
- Associated with tundra climate e.g. Iceland and northern edge of Europe and Asia.
d) Latosols
- Soils with low organic content and high titanium salts content which form in conditions of high rainfall and temperatures.
- Crumbles into dust if ploughed during dry season and cracks if not ploughed.
- Found in volcanic areas e.g. Uasin Gishu and Laikipia plateau.
e) Nitosols
- Deep porous friable red soils known as Kikuyu red loam in Kenya.
- Well aerated and high capacity for moisture storage.
- Higher fertility and can support a variety of cash and food crops.
f) Phenozems (Prairie Soils)
- Dark brown and generally fertile soils.
- Suitable for growing of cereals e.g. wheat.
- Common in Prairie Provinces of Canada, Narok and Athi-Kapiti plains.
g) Sierozems (desert soils)
- Soils found in desert conditions with little seasonal rainfall and high temperature.
- Relatively little humus due to sparse vegetation.
- Plenty of calcium carbonate inform of lime crust deposited on surface due to excessive evaporation.
h) Pedocals
- Dark soils which have had little leaching and rich in calcium carbonate.
- Common in semi-arid and sub-humid grasslands.
Sub-groups existing in Kenya
i) Chermozems
- Dark coloured soils with relatively high organic matter from grass vegetation and a calcareous sub-soil.
- Conducive for cereal crop cultivation due to being found in rolling land and favourable climate for grass growth.
- Found at bottom lands around Nyambene Hills and N. grazing areas between Isiolo and Nyambene Hills.
ii) Vertisols/Black Cotton Soils
- Dark cracking clay soils.
- Poorly drained due to high clay content leading to poor permeability.
- Suitable for growing of rice, cotton and sun flower.
- Found in Mwea plains and Kano plains.
2. Intrazonal Order
- Soil formed under poor drainage conditions.
Sub-orders
a) Hydromorphic soils
- Grey coloured soils formed in water logged areas.
Groups i) Plano soils - found on flat old land surfaces.
ii) Bog and meadow - found in meadows, marshes and swamps e.g. Lorian and Yala swamps.
b) Halmorphic Soils
- Soils formed under semi-arid and arid conditions through salinisation.
- Infertile and poorly drained.
- Found in Amboseli and N.E.Kenya.
c) Calcimorphic Soils
- Soils formed by calcification e.g. redzina soils which are shallow and rich in lime and humus on the upper profile
developed under grass on limestone e.g. in England and steppes of Russia.
d) Andosols
- Dark brown volcanic ash soils formed from recent volcanic material.
- High silt content and very vulnerable to soil erosion.
- Found in Kenyan highlands and support extensive agricultural activities like coffee, tea, wheat and maize growing.
3. Azonal Order
- Soils without a well developed profile due to having not undergone full soil forming processes.
- Found on steep slopes and areas with poor drainage which don’t offer them time to mature.
Sub-orders
a) Lithosols
- Soils with thin stony soil which is shallow over bedrock without a definite “B” horizon.
b) Regosols
- Soils without genetic horizons which have developed from material deposits like alluvium.
- Common in hilly and mountainous areas of the world.
c) Alluvial Soils (Fluvisols)
- Soils developed from alluvium of recent origin.
- Common along river valleys and mouths like Tana.
d) Mountain Soils
- Shallow soils found in mountainous regions.
- Vulnerable to erosion on steep slopes.
e) Histosols
- Soils formed from accumulation of organic matter which is 20% of the soil composition.
- If drained can be used to grow truck crops like vegetables.
f) Arenosols
- Soils having the appearance of sand largely composed of sand.
- Less fertile due to low organic matter.
- Common in coastal areas and N.E. provinces.