Ecological and Edaphic Drivers of Yam Production in West Africa

Yam is an important food and cash crop in West Africa (the yam belt) whose production is traditionally nonsedentary due to its substantial nutrient demand. Population growth, urbanization, and existing soil degradation have made nonsedentary farming virtually impossible. Despite the numerous research invested in yam production within and outside the yam belt, some gaps remain to be filled owing to changing climate events and global developments. Alarmingly, the yam belt is facing sharp yield declines despite increasing production areas. The key edaphic and ecological drivers of yam production in the global yam belt were reviewed. The implications for yam production were discussed along with prospects for future research, sustainable production, and soil management. The main findings are that (1) agroecological zone, postplanting cultural practices, and climate change and variability ecological drivers, while (2) tillage, soil type, texture, and fertility were the edaphic factors. The most critical among the drivers, principally, soil fertility, entails the biological and chemical through which nutrients are released lude, and physical soil fertility which enhances low bulk density, porosity, and water retention for free yam tuber expansion. Soil fertility was the most cited driver, which explains why yam is often the first crop in the cropland cultivation cycle in the yam belt. Data show that yam yields decline with time under native fertility and mineral fertilizer application due to the voracious nutrient extraction by tubers. Conversely, yields increase chronologically under organic fertilizer application due to the additive effects of the latter on soil properties. Thus, a yam fertilizer program to develop specific yam fertilizer formulations and the adoption of the Terra Preta Model are proposed to sustain future yam production.