A doctoral study at Kwame Nkrumah University of Science and Technology (KNUST) in Ghana compared ways of feeding two sweet potato varieties: the orange-fleshed CRI-Apomuden and the white-fleshed CRI-Dadanyuie. The work was led by Michael Odenkey Quaye of the Department of Crop and Soil Sciences.
Trials ran in two agro-ecological zones, on a University of Education, Winneba farm and at the CSIR Crops Research Institute field in Fumesua, alongside a survey of farmers in the Central Region. Seven soil treatments were tested, using mineral fertiliser, compost and biochar.
NPK fertiliser raised yields of the orange-fleshed variety by 54% to 68% compared with untreated plots, reaching almost 33 tonnes per hectare. A lower NPK rate combined with compost was also profitable. Biochar, about three times as expensive as compost, rarely paid off.
The researchers call for farmer training and policy support for integrated nutrient management, and say cheaper ways of producing biochar could make it more accessible in future.
