Écologie, systèmes de culture et utilisations alimentaires des ignames en Afrique tropicale : synthèse bibliographique.

This paper presents a literature review about botany, ecology, cropping systems, processing, constraints and prospects of sustainable yam production in tropical regions of Africa. Yam is a taxon of mainly tropical species requiring high temperatures. Germination is optimal between 25 and 30 °C, whereas temperatures below 15 °C or above 35 °C delay it. Yam is successfully cultivated in areas with rainfall ranging from 1000 to 1800 mm; however, it is possible to cultivate yam with a rainfall of only 600 mm, but yield remains low. To reach vegetative growth and good tuber formation, yam prefers sandy-loamy or loamy soils, with hydraulic conductivity of 15 cm/h, apparent soil density between 1.1 and 1.6 g.cm−3 and light and deep soils (> 0.6 m), well drained, rich in organic matter, nitrogen, potash, magnesium and calcium. A soil pH from 5 to 7 is suitable for a good yam production. Beyond the edaphic and climatic factors, cultivation practices, including cultivar, plantation density, date of planting, management of weeds, diseases and pests, cropping history of plots and farmers' soil management practices, affect yam productivity. Farmers base the choice of yam varieties mainly on culinary quality of tubers, productivity, commercial value, propagation, quality of chips, tuber formation precocity, conservation, facility of culture, roles as food and for ritual ceremonies. [ABSTRACT FROM AUTHOR]