(i) Coastal swamps/alluvial soil zone
(ii) Forest soil zone
(iii) Lateritic soil zone
(iv) Loess and sandy soil zone
Coastal Swamps or Alluvial Soil Zone
These types of soils are found along the coast of Nigeria in areas occupied by the Mangrove swamp forest i.e. Niger Delta areas of Warri, Port-Harcourt and Calabar.
They are also found along the flooded plains of rivers particularly the Niger and Benue coastal plains, Chad basin and Lokoja.
Alluvial soils are generally sandy, very previous and porous. Along the coastal swamps, the soils are usually day or muddy, this made them sticky and water logged. They are dark gray by rivers, waves and lakes since they are found mostly in the coastal areas, they are growth of variety of crops such as swamp rice, raffia palm and coconut in water logged areas, while in the valleys are smaller river crops like cocoyam and yams are grown.
RAIN FOREST SOIL ZONE
They are found in the tropical rain forest climatic zone of Nigeria, covering part of Enugu, Anambra, Ogun, Osun, Edo, Oyo, Ondo and Cross River state.
It is characterized by the feature of the tropical rainforest such as high temperature, high rainfall throughout the year, heavy cloud cover.
It is associated with the forest vegetation as the vegetation supplies humus to it through the fallen and decayed of leaves which as well protected it from erosion.
The rainforest soil zone contain laterictic soils which are characterized by excessive leading due to heavy rain fall, which lead to the removal of the nutrients even up to the sub soil (B-horizon) of the soil.
Forest soils are good and very suitable for the growth of some important crops as found in Nigeria like oil palm, rubber, cocoa, kolanut, etc.
LATERITIC SOIL ZONE
This type of soil has the largest area of covering in Nigeria as they are found occupying the interior part of country covering places like Benue, Kwara, Enugu, Plateau, Nigerm Kogi, Kaduna, Kebbi, Bauchi, Adamawa, Taraba etc.
They occur in areas with long period of dry season alternating with wet season, this they are synonymous to the Guinea savannah belt. Heavy leaching occur on the soil during the rainy season while capillary attraction takes place during the dry season.
They are generally reddish in colour due to the presence of iron content in them. They are sticky when wet, hard, pervious and of poor fertility when dry.
LOESS AND SANDY SOIL ZONES
These soil zones are found mainly in the extreme part of Northern Nigeria in places like Kano, Kastina, Bornu, Yobe, Jigawa, Sokoto and part of Kaduna occuring in the Sudan and Sahel savannah but of the country. They are formed directly from the parent material due to dryness and are transported and deposited by wind.
Growth of dense vegetation is abent due to little rainfall experience. The loess and sandy soils are composed of sandy, loam, friable and relatively easy to cultivate as they are not prone to much leaching. Crops like groundnut, millet, maize, guinea corn, cotton are widely grown. The absence of colloids in it make it loose and structureless and possesses grains which are coarse in texture.
PROBLEMS CONFRONTING SOILS IN NIGERIA
Major problems associated with soils in Nigeria are:
1. General lack of wide spread fertile soils in the country
2. A lot of the soils are seriously exposed to soil erosion as caused by agents of erosion like water and wind. This is mostly experienced in the Eastern and Nigeria states like Abia. Anambra, Imo, Ebonyi and Enugu. Other areas of soil erosion is the North-West of Nigeria (Kebbi and Sokoto). Bornu and Yobe in the North East of the country.
3. Lack of sufficient humus makes the soils unfertile thus affecting its productivity.
4. The threat of desert encroachment which is gradually overcoming Northern Nigeria.
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