Iron in the soil-plant-human continuum

Abstract

Iron (Fe) is essential for plants and animals and it is the fourth most common element and second most common metal in the Earth’s crust. In cultivated soils, Fe is mostly present in the Fe3+ and Fe2+ forms under oxic and anoxic environments, respectively. Iron should be present in the range >10-7.7 M in soil solution with a redox potential of soil-root environments under <12 to avoid its deficiency. The accessibility of Fe to plants is influenced by soil reaction, soil organics, aeration of the soil, presence or absence of other macro- and micronutrients, etc. Iron is required for the biogenesis and functioning of chlorophyll, energy transmission, metabolism of cells, fixation of nitrogen (N), and respiration of plants. Deficiency symptoms of Fe are first seen as the yellowish color between leaf veins, especially in young leaves, which could result in the necrosis at a later stage. Available soil test methods are not very effective in assessing available Fe in soils, whereas Fe2+ content in soil is a reasonably good predictor of plant Fe status. The supply of iron sulfate to the soil proved to be successful to eradicate Fe deficiency only when used along with compost and manure. As a comparison to soil application, foliar application of Fe had a major advantage to rectify its deficiency. To increase Fe level in edible parts of crops, agricultural techniques (e.g., agronomic biofortification and genetic biofortification) seem to be economic and efficient. The path to genetic biofortification is a long-term method that needs significant energy and money, but agronomic biofortification provides a simple solution to the overwhelming Fe deficiency problem. © 2021 Elsevier Inc. All rights reserved.