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

Commercial cocoa production in Nigeria is heavily concentrated in southwestern states such as Ondo, Osun, and Oyo, but is virtually absent in northern states like Kano and Sokoto. Which of the following environmental factors is the primary reason for this spatial limitation?

  1. The high mean annual rainfall exceeding 1,500 mm and sustained high relative humidity required by cocoa trees are restricted to the southern rainforest belt.Answer
  2. B
    The high prevalence of tsetse flies in the northern savanna, which transmit diseases that destroy perennial tree crop root systems.
  3. C
    The presence of rich, volcanic clay soils in the northern savanna which are too dense for tree crop root penetration.
  4. D
    Severe sub-zero frost conditions during the Harmattan season in the north that freeze plant tissues.

Answer

Cocoa cultivation requires high mean annual rainfall (1,500–2,000 mm) and high relative humidity, environmental conditions characteristic of the humid tropical forest zone of southwestern Nigeria but lacking in the semi-arid northern savanna.
Cocoa is a humid tropical tree crop whose growth demands high annual rainfall (exceeding 1,500 mm) and elevated relative humidity. Southwestern states (Ondo, Osun, Oyo) lie within Nigeria's tropical rainforest belt where these moisture conditions prevail, whereas northern states (Kano, Sokoto) lie in semi-arid savanna zones with long dry seasons.

Step-by-Step Solution

1
Identify the crop and its ecological requirements
Cocoa (Theobroma cacao) is a tropical tree cash crop requiring warm temperatures, high annual rainfall (>1,500 mm>1,500\text{ mm}), and high relative humidity.
Perennial tree crops of tropical origin cannot withstand prolonged severe moisture deficits or low atmospheric humidity.
2
Analyze the spatial climate gradient of Nigeria
Rainfall and relative humidity decrease along a south-to-north latitudinal gradient across Nigeria, moving from the rainforest belt in the south to the Sudan/Sahel savanna in the north.
The influence of the Tropical Maritime (mT) air mass weakens northwards, resulting in shorter rainy seasons and lower total precipitation in the north.
3
Evaluate the environmental constraint limiting northern cultivation
The long dry season (5–8 months) and low rainfall (<1,000 mm<1,000\text{ mm}) in northern states like Kano fail to satisfy cocoa moisture requirements.
Moisture availability during the growing season is the primary environmental determinant separating southern tree crop belts from northern grain/livestock belts.

Key Concept

Ecological Adaptation and Spatial Zonation of Nigerian Crops
Estimated Time:1m 0s
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Topics

Agricultural Systems, Crop Production, and Pastoralism in Nigeria

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