Foliar Absorption and Translocation of Metal-Amino Acid Complexes in Soybean: A Case Study of Manganese, Zinc, Glutamate, and Histidine

The mixture of amino acids and mineral nutrients has already been employed by farmers to improve the efficiency of foliar fertilization, although systematic studies to support the practice are scarce. We deployed an in vivo X-ray fluorescence spectrometry setup to measure the uptake and short-range transport of Mn and Zn complexed with histidine and glutamate. As positive controls, we used stand-alone amino acids and sulfate-based micronutrients. The results showed that under high relative humidity (70–86%), the histidine and glutamate complexes presented transport performance similar to that of sulfates. However, under nonoptimal relative humidity (35–45%), the amino acid complexes presented twice the transport of sulfates. The glutamate complex increased the concentration of Mn in the treated tissue by 670 mg kg–1; it also induced higher translocation of Mn and Zn to older leaves. The complexes also reduced the phytotoxicity. Thus, the study concludes that such types of biocomplexes offer advantages over standalone salts.