(a) State four characteristics of a fertile soil. (4 marks)
(b) Discuss briefly three factors that affect land availability for agricultural production in West Africa. (6 marks)
(c) State four benefits of draining farm lands (4 marks)
(d) List two sources of soil nitrogen. (2 marks)
Explanation
3(a) Characteristics of fertile soil:
-Rich in plant nutrients
-Percolation of water is low.
-Capillarity is high
-Well aerated.
-Leaching is Low.
-Good water holding capacity.
-Normally neutral in nature.
-Easily worked/cultivated in both dry and wet forms.
-Contains decayed organic matter/humus.
-Normally dark-brown or black
-Contains soil micro organisms.
(b) Factors that affect land availability for production in West Africa
(i) Land Tenure System Prevailing system of land ownership does not encourage prospective farmers to acquire large hectares of land
(ii) Population pressure/size: Land tends to be available where the population is very low, such as in the rural areas. But land will not be available where the population is high such as in urban areas.
(iii) Size of useful land: The size of land ideal for agriculture will also affect its usage. In deserts, mountainous areas and savannahs, the size of land for agriculture will be small.
(iv) Climate: Climatic factors such as rainfall, relative humidity, temperature and day length affect the availability of land for crop and livestock production and distribution in an area.
(v) Religious beliefs: Type of religious beliefs practised in an area will affect land usage. For instance, presence of sacred forests or grooves and rearing of pigs in a muslim dominated area, make land unavailable for agricultural production.
(vi) Soil factor/ type: The type of soil in an area determines the availability of land for farming. The productivity or fertility of the land also determines the type of crops to be grown on it.
(vii) Topography: Refers to the shape of the land surface. The land may be sloping, undulating or flat. Highlands (hilly/mountainous) do not make land available for agriculture since they are prone to erosion. Flat or gentle sloping land is suitable for agricultural purposes since it is less prone to erosion.
(viii) Farming systems: The type of cultivation methods practised in a place will also account for land availability. Cultural methods like bush fallowing, shifting cultivation and deforestation are detrimental to agricultural production.
(ix) Infrastructural demands on land: Demand on land for road construction, buildings, recreational centres, cinemas, etc reduces land available for agriculture.
(x) Government policy: Government may legislate from time to time on the nature and usage of land e.g. land use decree/act/policy which may not encourage the availability of land for agriculture.
(c) Benefits of draining farm lands:
(i) Facilitates early planting.
(ii) Protects soil from water logging.
(iii) Improves soil aeration.
(iv) Improves/increases soil temperature.
(v) Allows for cultivation practices.
(vi) Favours the growth of beneficial bacteria and other soil organisms.
(vii) Means of reclaiming lands for agricultural purposes.
(viii) Leaches out excess salts from soils.
(ix) Enhances seed germination.
(x) Prevents toxicity of plants.
(xi) Provides more soil moisture and plant nutrients.
(xii) Increases the depth of root zones in the soil.
(xiii) Helps to increase decomposition of plants and animal residues.
(xiv) Enhances water infiltration into the soil
(xv) Regulates soil pH
(xvi) Improves soil structure and increases soil productivity.
(xvii) Reduces the incidence of diseases of crops.
(xviii) Reduces the incidence of pests of crops.
(d) Sources of soil nitrogen:
(i) Use of nitrogeneous fertilizers such as urea, ammonium sulphate, etc.
(ii) Symbiotic and non-symbiotic nitrogen fixation/biological fixation.
(iii) Nitrification of certain compounds by nitrobacter and nitrosomonas.
(iv) The action of thunder and lightening (chemical fixation).
(v) Use of organic manures like compost, green manure, etc.