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Difficulty: HardAgricultural Systems, Crop Production, and Pastoralism in Nigeria

Although irrigated paddy rice and sugarcane yield abundant harvests in the river floodplains (fadama) of Sokoto and Niger states, commercial perennial tree crops like cocoa and rubber cannot be successfully cultivated in these regions. Which environmental constraint primarily accounts for this agricultural boundary?

  1. The prolonged dry season and low atmospheric humidity in northern river basins exceed the ecological tolerance of rain forest tree crops.Answer
  2. B
    The high prevalence of tsetse fly infestation along northern river valleys destroys tree crop foliage during the dry season.
  3. C
    The fertile alluvial soils of fadama floodplains contain excessive acidity that stunts the root systems of deep-rooted tree crops.
  4. D
    The high elevation and low winter temperatures of northern river basins cause frost damage to tropical tree crops.

Answer

The prolonged dry season and low atmospheric humidity in northern river basins exceed the ecological tolerance of rain forest tree crops.
Perennial tree crops like cocoa, oil palm, and rubber are strictly adapted to the tropical rainforest belt of southern Nigeria, requiring high annual rainfall exceeding 1,500 mm1,500\text{ mm} and high relative humidity throughout the year. While irrigation in northern floodplains (fadama lands) provides sufficient moisture for annual grain and vegetable crops like rice and sugarcane during their growing cycle, it cannot alter the prevailing low atmospheric humidity and extended dry season of the savanna belts, which inhibit tree crop development.

Step-by-Step Solution

1
Analyze the agricultural requirements of the crops mentioned in the scenario.
Paddy rice and sugarcane are annual or semi-perennial crops that can flourish in northern floodplains (fadama) if supplemental water is supplied via seasonal flooding or irrigation. Cocoa and rubber are permanent tree crops requiring persistent humid forest climates.
Understanding crop ecological limits distinguishes irrigated annual cropping from rain-fed tree crop belts.
2
Evaluate the climatic envelope of northern Nigeria (Sudan and Northern Guinea Savanna).
The region features a short wet season (3–5 months3\text{--}5\text{ months}), long dry season (7–9 months7\text{--}9\text{ months}), low relative humidity under the Influence of dry Harmattan winds, and annual rainfall well below 1,000 mm1,000\text{ mm}.
Climatic controls dictate the spatial limits of commercial tree crop belts across Nigerian ecological zones.
3
Identify why irrigation overcomes limits for grains/vegetables but not tree crops in northern zones.
Irrigation solves root water availability in river floodplains, but cannot compensate for low atmospheric humidity and extreme vapor pressure deficits that disrupt tree transpiration and physiological growth in cocoa and rubber.
This confirms atmospheric drought as the primary ecological barrier for rain forest tree crops in northern Nigeria.

Key Concept

Ecological controls on Nigerian crop belts and fadama agricultural systems
Estimated Time:2m 0s
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Topics

Agricultural Systems, Crop Production, and Pastoralism in Nigeria

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