SAHEL WEATHER AND CROP SITUATION 1999Global Information and Early Warning System on food and agriculture
Report No 4 - 10 September 1999
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Following generally above normal rains in July over most agricultural zones, growing conditions remained favourable in August in the Sahelian countries. During the three dekads of August, rainfall was generally above normal and cumulative rainfall in August exceeds 100 mm everywhere in the main producing zones of the Sahel and in most cases in northern desert areas (see map on page 4). Unusually heavy rains were registered in Burkina Faso, Chad, Gambia, Mali, Mauritania, Niger and Senegal, causing substantial flooding. These abundant rains benefited crop and pasture development particularly in Mauritania, northern Senegal and Mali, although excess water may reduce yield potential in flooded fields in low-lying areas. Crop prospects are generally favourable. However, the outcome for long cycle varieties in the Sudanian zones (Burkina Faso, Niger and Chad) will depend on the continuation of the rains in September. Pastures are abundant in the region. Satellite imagery for the first days of September indicates that precipitation decreased somewhat over the Sahel but remained widespread and still above average over most parts of Burkina Faso and Chad.
Pest infestations (mostly grasshoppers and army worms) are reported in Cape
Verde, Niger and Senegal, and treatments have been undertaken in some areas.
Stemborers caused damage on millet in northern Burkina Faso. Although no Desert
Locusts have been reported from any country in the region, small-scale breeding
may occur. No significant developments are expected.
BURKINA FASO CAPE-VERDE CHAD GAMBIA GUINEA-BISSAU
MALI MAURITANIA NIGER SENEGAL
In these reports, reference will be made to four different eco-climatic zones based on the average annual precipitation and agricultural features, i.e. Sahelian zone, Sudano-Sahelian zone, Sudanian zone and Guinean zone. They are shown in the map and described below:
Sahelian zone: Where average annual precipitation ranges between 250 and 500 mm. This zone is at the limit of perennial vegetation. In parts where precipitation is less than 350 mm, only pastures and occasional short-cycle drought-resistant cereal crops are grown; all cropping in this zone is subject to high risk.
Sudano-Sahelian zone: Where average annual precipitation ranges from 500 to 900 mm. In those parts of this zone where precipitation is less than 700 mm, mostly crops with a short growing cycle of 90 days are generally cultivated predominantly sorghum and millet.
Sudanian zone: Where average annual precipitation ranges from 900 to 1 100 mm. In this zone, most cereal crops have a growing cycle of 120 days or more. Most cereals, notably maize, root and cash crops are grown in this zone.
Guinean zone: Where average annual precipitation exceeds 1 100 mm. Guinea-Bissau and a small area of southern Burkina Faso belong to this zone, more suited to root crop cultivation.
Reference will also be made to the Intertropical Convergence Zone (ITCZ), also known by its trace on the earth's surface, called the Intertropical Front. The ITCZ is a quasi-permanent zone between two air masses separating the northern and southern hemisphere trade winds. The ITCZ moves north and south of the equator and usually reaches its most northerly position in July. Its position defines the northern limits of possible precipitation in the Sahel; rain-bearing clouds are generally situated 150-200 km south of the Intertropical Front.