Application of different foliar iron fertilizers for improving the photosynthesis and tuber quality of potato (Solanum tuberosum L.) and enhancing iron biofortification

Abstract Background The potato (Solanum tuberosum L.) is an important food crop in the alkaline soil area of northwest China. It is abundant in ascorbic acid (vitamin C), which facilitates iron absorption in the body. The large consumption of potato makes it a good food source of iron absorption for human body. However, iron deficiency in alkaline soil regions reduced chlorophyll synthesis in the leaves, resulting in lower photosynthesis and less sugar supply to the plant's healthy organs, significantly restricted crop development and yield, and inflicted major economic losses. Methods In this study, a 2-year (2020–2021) field trial was designed. Under foliar application of five different iron fertilizers: ferric sulfate [(Fe2(SO4)3], T1; ferrous sulfate (FeSO4·7H2O), T2; citric acid/ferric sulfate (CA/Fe2(SO4)3), T3; citric acid/ferrous sulfate (CA/FeSO4·7H2O), T4; ethylenediamine tetra acetic acid (EDTA-Fe·Na), T5, changes in potato plant photosynthesis were compared to no iron fertilization, CK conditions. The effects of various iron fertilizers on the yield, quality, and iron content of potato tubers, their correlations to chlorophyll levels, and the characteristics of photosynthetic fluorescence were studied. Results The results indicated that spraying iron fertilizers increased the yield, quality and Fe content of the tubers, which might be due to the improvement of the plants’ photosynthetic pigment content, gas exchange parameters and chlorophyll fluorescence. In two consecutive years of cultivation, we found that potato tuber yield and Fe content increased in potatoes treated with five iron fertilizer sprays. Among them, tuber yield increased most significantly by T5 and T3 treatments compared to CK, while Fe content was significantly higher by the T5 treatment than by CK and other treatments. Tuber yield was increased by 33.28% and 18.85% in 2020 and 50.74% and 54.48% in 2021 by T5 and T3 treatments, respectively, compared to CK. Fe content was increased by 112.64% and 54.98% in 2020 and 2021 by T5 treatment, respectively, compared to CK. Conclusions EDTA-Fe·Na and CA/Fe2(SO4)3 excelled over the other iron fertilizers. The findings of this study are instructive for developing cost-effective iron fertilizer management systems to maximize the impact of iron biofortification on human health. Graphical Abstract