Biofortification of finger millet with zinc and iron under biochar amendment: Effects of soil and foliar fertilization on yield and grain quality

Abstract Biofortification is an effective strategy to improve the micronutrient content of staple crops. However, biofortification of finger millet ( Eleusine coracana L .) with zinc (Zn) and iron (Fe) has not been adequately investigated under biochar amendment. Pot experiments were conducted in Gulu, Uganda, during the years 2022 and 2023 to evaluate the effects of soil and foliar application of Zn and Fe fertilizers on grain yield and quality of finger millet grown in biochar‐amended Alisol and Ferralsol. Treatments included Zn and Fe fertilizers applied individually and in combination through soil and foliar methods under biochar amendment. Biochar application significantly increased grain yield by 79% in Alisol and 185% in Ferralsol compared to the non‐biochar control. Foliar applications of a combination of Zn and Fe fertilizers increased grain yield by 61% and 24% under Alisol and Ferralsol, respectively, compared to soil application. Zinc fertilization significantly enhanced grain Zn concentration relative to the untreated control in both soil types. In Ferralsol, foliar application improved grain Zn content by 11% compared to soil application, whereas no difference was observed in Alisol. Grain Fe concentration showed variable responses depending on soil type and treatment. Overall, while biochar improved grain yield, its effect on Zn and Fe enrichment was not consistent across treatments and soil types. These findings suggest that the effectiveness of Zn and Fe biofortification in finger millet under biochar amendment depends on soil type and fertilizer application method.