The root and tuber crop farming system: diversity, complexity and productivity potential

Abstract

The root and tuber crop farming system occurs in west and central Africa, bounded on the southern, wetter side by the tree crop farming system and on the northern, drier side by the cereal-root crop mixed farming system. The root and tuber crop farming system occupies an estimated 236 million ha and has an estimated human population of 112 million, of whom over 50 per cent live in rural areas. Poverty is relatively high with about half the rural population earning less than US$1.25 per day. The system has a humid tropical climate with, on average, a nine-month growing season. These climatic conditions support the characteristic root and tuber crops (cassava, cocoyam, yam and sweet potatoes) complemented by some tree crops (oil palm, cocoa, rubber, cashew and mangoes) and cereals (maize, rice, sorghum and millet) and small numbers of livestock – making it a highly diverse and complex farming system with stable and relatively high potential food productivity. The farming system is at an early stage of development, mainly focused on household food security. Markets are generally poorly developed, although there are pockets of semi-commercial farming. Total cultivated area is nearly 23 million ha, of which little is irrigated. Farm sizes are generally small, usually less than 2 ha. Crop production is mostly subsistence. Female members of farm households have an important role in the farming system, especially in the production and processing of root and tuber crops. The farming system has great potential because of its high biomass productivity combined with its suitability for commercial tree crops, root and tuber crops as well as horticulture, and proximity to major urban centres and export ports. In coming years, the system is expected to expand production of tree, root and tuber crops to meet the food needs of a rapidly increasing urban population. Increased productivity requires wider use of high-yielding crop varieties coupled with integrated soil fertility management (ISFM) to replenish declining soil fertility. Strategic priorities for the sector include market-oriented intensification through the use of improved varieties and ISFM technologies, complemented by diversification to include cereals, other annual crops and ruminant production. This intensification and diversification requires farmer training, increased research and extension capacity, investment in transport and market infrastructure, and national policies that promote roots and tubers as both food security and industrial crops supported by public-private partnerships.