ABSTRACT
The rapid increase in population and consequent pressure for food are driving agriculture towards greater intensification in West Africa
(Sanginga et al., 2003). The long fallow periods have not only diminished but also agriculture has now been pushed onto marginal lands, leaving little or no scope for further expansion in the cultivated area. This is more pronounced in the dry savannas of West Africa where rainfall is low and soils are predominantly sandy with low organic matter, low phosphorus and poor water holding capacity. Also, agriculture in this region is still based on traditional inter-cropping of cereals like maize (Zea mays L.), sorghum [Sorghum bicolor (L.) Moench] and pearl millet (Pennisetum glaucum), with a cowpea arrangement involving 1-row cereal-l-row cowpea [Vigna unguiculata (L.) Walp.] with a low plant density and little or no application of fertlizers and chemicals (Norman, 1974; Baker and Norman, 1975; Edwards, 1993; Mortimore et al., 1997; Henriet et al., 1997). The FAO estimates (FAO STAT-2004) indicate that West Africa uses about 8 kg fertilizer/ha annually compared with 100 to 400 kg/ha in other countries (Table 1). Such practices lead to decreased soil organic matter, increased populations of chronic parasitic weeds (e.g., Striga spp.), reduced soil biological diversity and enhanced erosion risk. This, in turn, leads to a negative balance of nutrients in the soil and continuous decline in crop yields. Recent estimates indicate that the annual nutrient losses exceed 26 kg of N, 3 kg of P, and 19 kg K per hectare (Sanginga et al., 2003). Consequently, in this system, the cereal yields are low due to low fertility and cowpea yields are low due to shading from cereals throughout the growing period and thus the overall grain as well as fodder productivity of both cereals and cowpea is drastically reduced. Even though cowpea occupies 50% of the land area under intercropping, its yield is usually less than 25% of the sole crop and farmers obtain less than 1 ton of total food per hectare (van Ek et al., 1997), which perpetuates poverty through the vicious circle of ‘low input-low production-low income’ and consequent food insecurity. Presently, over 70% of the population in West Africa lives below the poverty line, spending less than one dollar a day. The widely reported food crisis in 2005 in Niger Republic is an example of this problem. How to help them and reverse this trend?
