Crop–Livestock Interactions in the West African Drylands

crop production technologies. In many regions, livestock are also a means of storing capital, of buffering Many semiarid regions of Sub-Saharan Africa (SSA) are experiencfood shortages in years of poor crop production, and of ing vast increases in human population pressure and urbanization. meeting social and religious obligations of farmers. These augment the demand for agricultural products and have led to In these systems, the productivities of livestock, rangethe expansion, intensification, and often closer integration of crop and livestock production systems. The transition of crop and livestock lands, and croplands are inextricably linked. Although production from the current relatively extensive, low input/output most agricultural products are used for subsistence purmodes of production to more intensive, higher input/output modes poses, some outputs of rangeland (wood, bush straw, of production presents numerous challenges to the achievement of and fruits), cropland (grains, crop residues, and legume required long-term production increases from these farming systems. hays), and livestock (animals, milk, meat, and skins) are This paper provides an overview of the challenges facing agricultural sold. Crop residues are vital livestock feeds during the production in semiarid SSA with a focus on West Africa. A description 6 to 8 mo dry season, and manure enhances soil fertility of mixed crop–livestock farming systems and their evolution is folfor crop production. Natural forages from rangelands lowed by an overview of the principal linkages between crops and and fallow lands provide important livestock feeds and, livestock: income, animal power, feed, and manure. The most detailed through manure, nutrients for cropland. Manure is obdiscussions relate to nutrient cycling in these farming systems. Most livestock derive their feed almost exclusively from natural rangeland tained from either one’s own livestock, from the liveand crop residues, and livestock manure is a precious soil fertility stock of other farmers, or through exchange relationships amendment. However, most farmers have insufficient livestock and with pastoralists. Manure contracts between farmers therefore manure to sustain food production. Nutrient harvests from and pastoralists are still important in many West African cropland often exceed nutrient inputs, and soil nutrient depletion is dryland areas, and farmers have developed a variety of a principal concern. The paper concludes with a discussion of strategies ways to combine their own smaller herds to manure that may improve the productive capacity of these mixed farming large cropland areas. systems. A principal challenge facing agriculture in many parts of SSA is how to achieve sustainable increases in crop and livestock production with limited use of fertilizers M dryland farming systems of SSA integrate and feed supplements. Farmers continue to rely princicrop and livestock production. Pearl millet [Penpally on organic matter recycling to maintain soil fertilnisetum glaucum (L.) R. Br.], sorghum [Sorghum bicolor ity. However, the harvest of N, P, and K exceeds the (L.) Moench], and maize (Zea mays L.) are the principal input of these nutrients, and yields appear to be declincereals, fonio [Digitaria exilis (Kippist) Stapf] is imporing. Low rural incomes and the high cost of fertilizer tant in some areas, and rice (Oryza spp.) is cultivated and feed supplements, among other factors, prevent the in delta areas and along river and stream borders. The widespread use of these external nutrient sources. The legumes cowpea [Vigna unguiculata (L.) Walp.] and use of fertilizer is limited to small land areas devoted groundnut (Arachis hypogaea L.) are both subsistence to cash crops, and diet supplements for livestock are and cash crops; grain and hay may be sold. Household used scantly in semi-intensive livestock-fattening operalivestock holdings range from a few to hundreds of head tions around urban areas and for fattening animals beper household with varying ratios of cattle, sheep, and fore religious and social festivals. Animal manure is goats (Wilson, 1986; Swinton, 1988). In some areas, escurrently perhaps the most important soil fertility amendpecially associated with cash crop production, cattle, ment. As long as fertilizers and feed supplements are donkeys, horses, and camels provide draft power for unavailable, the fertility of cropland will continue to tillage, crop planting, weeding, crop harvest, processing, depend on the nutrients supplied from rangeland in the and transport. Livestock also provide meat and milk for form of manure. households and cash income that is often invested in The climatic and socioeconomic changes occurring in many parts of SSA are rapidly transforming traditional, extensive crop and livestock management practices, J.M. Powell, U.S. Dairy Forage Res. Cent., USDA-ARS, 1925 Linden Drive West, Madison, WI 53706; R.A. Pearson, Cent. for Trop. Veteribased on shifting cultivation and transhumance, to more nary Medicine, Easter Bush, Roslin, Midlothian, EH25 9RG, UK; sedentary forms of production. Problems common to and P.H. Hiernaux, Int. Livestock Res. Inst., B.P. 12404, Niamey, these agricultural systems include inadequate feed reNiger. Received 5 March 2003. *Corresponding author (jmpowel2@ sources, encroachment of cropping on grazing lands, wisc.edu). reduced fallow periods (resulting in declining soil fertilPublished in Agron. J. 96:469–483 (2004).  American Society of Agronomy 677 S. Segoe Rd., Madison, WI 53711 USA Abbreviations: SSA, Sub-Saharan Africa.