Vanadium Management

This element may be beneficial in low concentrations.

Vanadium in the Soil

Vanadium (V) is a transition metal found naturally in small amounts. Anthropogenic inputs such as mining can cause high concentrations of V to accumulate in certain areas, toxifying the soils. Vanadium pentoxide (V2O5) is the most common usable form of vanadium. It can also be found as ammonium metavanadate (NH4VO3), sodium metavanadate (NaVO3), and sodium orthovanadate (Na3VO4). Soil properties determine the dominant oxidation states present. Vanadium can range in oxidation state from +2 to +5. In reducing environments, it is commonly found as V +4 (or vanadyl). In aerobic environments, V +5 prevails, forming vanadate (H2VO4-) above pH 4 and VO2+ below pH 4.

The sorption strength of the soil is the primary determining factor of the toxicity of vanadium. Vanadium adsorbs strongly to iron and aluminum oxides and hydroxides and can form complexes with organic matter like clays. When bound to organic matter, vanadium(V) can be reduced to less mobile vanadium(IV). Vanadium adsorbed to these compounds is not bioavailable. Hence, the total V content of the soil is not a good indicator of V toxicity. The amount of V in soil solution is a more accurate indicator.

Vanadium in the Plant

Vanadium +5 is more mobile than vanadium +4 and is taken up by plants at a much greater rate. Within the plant, V +5 can generate high levels of ROS and may even cause damage to chromosomes. As roots take up V +5, they can oxidize organic molecules found in the cell wall and be reduced to V +4, immobilizing it within root tissues. Little vanadium is transported aboveground. In rapeseed, the concentration of V in the leaves was only 0.63 mg/kg, which was undetectable in the seed, whereas it was 6.46 mg/kg in the roots.

While V is a required nutrient for some organisms, no concrete evidence supports plant necessity. Studies have shown that concentrations of vanadium as low as 2 mg/kg may increase certain plants’ metabolic activity and growth rates. Concentrations above 2 mg/kg damage plant health. Vanadate is structurally similar to phosphate and can be mistakenly substituted for phosphate in many enzymatic reactions. It can both inhibit and stimulate specific metabolic pathways. V is known to inhibit the activity of active transport proteins like the Na+/K+ pump and the proton pump, which are necessary for nutrient uptake. It also interferes with protein synthesis and chlorophyll production.

Further Reading

Imtiaz, M., Rizwan, M. S., Xiong, S., Li, H., Ashraf, M., Shahzad, S. M., Shahzad, M., Rizwan, M., and Tu, S. (2015). Vanadium, recent advancements and research prospects: a review. Environment International.

Larsson, M. A., Baken, S., Gustafsson, J. P., Hadialhejazi, G., and Smolders, E. (2013). Vanadium bioavailability and toxicity to soil microorganisms and plants. Environmental Toxicology and Chemistry.

Roychoudhury, A. (2020). Vanadium uptake and toxicity in plants. SF Journal of Agricultural and Crop Management.

Tian, L., Yang, J., and Huang, J. (2015). Uptake and speciation of vanadium in the rhizosphere soils of rape (Brassica juncea L.). Environmental Science and Pollution Research.

Yang, J., Wang, M., Jia, Y., Gou, M., and Zeyer, J. (2017). Toxicity of vanadium in soil on soybean at different growth stages. Environmental Pollution.