Theory question 103
Irrigation and Drainage(a) Mention two sources of irrigation water.
(b) Enumerate two advantages and two disadvantages of irrigating farmlands.
(c) List two ways by which the soil loses nutrients.
(d) Give two reasons for manuring in crop production.
(e) State two ways by which each of the following environmental factors affect agricultural production: (i) temperature; (ii) soil microorganisms; (iii) wind
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(a) Any two: rivers and streams; lakes/ponds; dams and reservoirs; wells and boreholes; rain water harvesting.
(b) Advantages: all-year cropping; higher yields; makes dry land usable; can carry fertilizer. Disadvantages: costly to install and run; waterlogging; salt build-up; spreads water-borne diseases/weeds; erosion if poorly managed.
(c) Any two: leaching; erosion; crop removal (harvesting); burning; volatilisation/denitrification.
(d) Any two: supply nutrients; improve soil structure and water holding; increase soil organisms; buffer soil pH.
(e)(i) Temperature: affects germination, growth and flowering; affects distribution of crops and animals; high temperature causes heat stress and evaporation; affects rate of photosynthesis and respiration.
(ii) Soil microorganisms: decompose organic matter and release nutrients; fix nitrogen; some cause diseases of crops; improve soil structure.
(iii) Wind: disperses pollen and seeds; causes lodging of crops; increases evaporation and transpiration; causes wind erosion; spreads pests and diseases; drives windmills.
Two effects for each of the three factors in (e).