This question was fairly popular among the candidates. In 3(a), majority of the candidates were able to mention sources of irrigation water but were unable to enumerate the advantages and disadvantages of irrigating farmlands as required in 3(b). Further to this, most of the candidates were able to list ways by which the soil loses nutrients as required in 3(c) but majority of them could not give reasons for manuring in crop production as required in 3(d). Also, majority of the candidates were unable to state the ways by which environmental factors affect agricultural production as required
in 3(e).
The expected answers include:
(b) Advantages and disadvantages of irrigating farmlands
Advantages
- Makes early planting possible
- Adds water to the soil/supply moisture to the soil for plant growth
- Helps to soften the soil for easy tillage operations
- Facilitates the survival of crops during drought
- Farmers become less dependent on rainfall
- Helps lower soil temperature
- Ensures all-year-round production
- Modifies both soil and plant environment
- Enhances microbial decomposition of organic matter in the soil
- Dissolves nutrients for root absorption
- Can be used to apply liquid fertilizers(fertigation)
Disadvantages
- High cost of irrigation equipment
- Increased salinity
Disease transmission is possible
- Leads to build-up and spread of pests
- Vectors of diseases e.g. snails, tsetse flies, mosquitoes may breed in
irrigated areas
- Movement of farm machinery may be hindered
- May lead to leaching
- May lead to erosion/flooding
- Encourages the growth and spread of weeds
(d) Reasons for manuring in crop production
- Improves the activities of soil organisms like earthworms
- Improves the structure of the soil
- Improves aeration within the soil
- Regulates soil temperature
- Buffering effects improve the acid-base reaction of the soil/assists in regulating soil pH
- Improves water holding capacity in sandy soil
- Improves water infiltration in clay soil
- Controls soil erosion
- Adds nutrients to the soil/improves soil fertility
- Increases cat ion exchange capacity of the soil
- Used for the control of nematodes in the soil
(e) Ways by which environmental factors affect agricultural production
- Temperature
- High temperature may cause heat stress/death of farm animals
- A necessary condition for germination of seeds
- Affects distribution of crops
- Affects distribution of animals
- High temperature increases evapo-transpiration
- High temperature reduces the performance of livestock/fish
- Temperature affects the ripening and maturity of fruits
- Affects microbial activities in relation to mineralization of organicsubstances
-
Temperature affects productivity of human labour/draught animal
Soil micro-organisms
- Cause diseases in plants
- Bacteria in root nodules can fix nitrogen directly to plants and soils
- Reduce the quantity and quality of crops e.g. potato, yam
- Help in the decomposition of plant materials to form humus
ii)Wind
- Influences the rate of transpiration
- Causes evaporation in the soil
- May cause lodging of plants
- High wind velocity may cause soil erosion in dry/arid areas
- Important in rainfall distribution and pattern
- Important in fruits/seeds dispersal
- Assists in crop pollination
- Causes mechanical injury to crops e.g. loss of leaves, branches,
flowersand fruits
- Causes spore dispersal or spread of diseases
- Partly determines seasons.
