Enhancing Nutrient Composition and Bioavailability in Common Beans Using Combined Zinc and Iron Fertilizers

Agronomic biofortification is the quickest and most cost-effective approach to addressing zinc (Zn) and iron (Fe) deficiencies, especially as climate change presents growing public health issues in developing countries.

This investigation aims to evaluate the effect of different rates of combined Zn and Fe fertilizers on phytic acid (PA) levels, the ratios of PA-Zn and Fe, and the proximate composition of common bean varieties.

The field experiment was conducted at Melkassa Research Center and the Negelle Arsi sub-stations by utilizing a split plot design, consisting of twenty-seven treatments that were replicated three times. Three bean varieties (DAB-197, SAB-632, and BZ-2) and nine Zn+Fe fertilizer rates (T1 = control, T2 = 0+1.5%, T3 = 0+3%, T4 = 0.5%+0, T5 = 0.5%+1.5%, T6 = 0.5%+3%, T7 = 1%+0, T8 = 1%+1.5%, and T9 = 1%+3%) were included in treatments.

The combined results of the two sites indicated that both varieties and fertilizer treatments significantly (P< 0.05) influenced proximate composition, antinutrient content, and PA: Zn and Fe molar ratios. Among the bean varieties, DAB-197 exhibited the highest (23.2%) crude protein content. Meanwhile, the SAB-632 variety showed a sufficient amount of ash and crude fiber content. The SAB-632 variety had the lowest PA: Zn ratio among the varieties. Higher rates of Zn and Fe fertilizers significantly reduced PA levels and molar ratios, with the lowest values in treatment T9.

These results indicate that increased applications of Zn and Fe improve nutrient bioavailability. Therefore, the DAB-197 and SAB-632 varieties, treated with Zn and Fecontaining fertilizers, could serve as alternative nutrient sources to tackle widespread micronutrient deficiencies in developing countries, including Ethiopia.