Organic-Microbial Strategies for Iron and Zinc Biofortification in Orange-Fleshed Sweet Potato [Ipomoea batatas (L.) Lam.].

Orange-fleshed sweet potato (OFSP) is widely promoted in sub-Saharan Africa, including Senegal, for its contribution to vitamin A deficiency mitigation. However, its potential to improve mineral nutrition remains limited by low iron (Fe) and zinc (Zn) concentrations and their restricted bioavailability, which may contribute to persistent micronutrient deficiencies affecting 42% of children under 5 years and 37% of women of reproductive age in Senegal. In this context, organic waste products (OWPs) and microbial inocula (MIs) represent promising agroecological alternatives to conventional fertilizers for enhancing the nutritional quality of OFSP while valorizing locally available resources. This study aimed to evaluate the combined effects of various OWPs and MIs on tuber yield and Fe/Zn concentrations in OFSP within an agroecological production system. Field experiments were conducted across two contrasting seasons: a rainy season (June 2021-November 2021), followed by a dry season (December 2021-May 2022). The OFSP variety used was "Apomudem". Two types of MIs were tested: local beneficial microorganisms (BMs), a bacterial-fungal consortium derived from fermented forest litter, and mycorrhizal fungi (MF; Glomus mosseae). A factorial arrangement in a randomized complete block design with four replications was employed. Results revealed several combinations that significantly improved both yield and micronutrient content. The treatment combining poultry litter (PL) with BMs yielded 21 t ha-1 of tubers-a 2.6-fold increase compared to the unfertilized control-and doubled Zn concentration to 20 mg kg-1 DM. Additionally, the combination of PL, BMs, and MF increased Fe concentration to 44 mg kg-1 DM, a 1.7-fold increase. These effects varied with OWP and inoculum type, confirming that their interactions strongly influenced nutrient enrichment. Overall, combining OWPs with microbial inocula provides an effective agroecological approach for enriching crops with essential micronutrients and opens promising avenues for improving staple crop productivity and nutritional quality by effectively valorizing locally available resources, supporting agroecological transition, and food security.