Nutrient and elemental toxicities

Contamination of agricultural soils by potentially toxic elements (PTEs) is widespread all over the world due to the intensification of crop production and rising anthropic inputs in agriculture and the environment. Depending on the concentration and speciation of these elements in soil, especially in the rhizosphere, and on the plant species, significant amounts of toxic elements can be taken up by roots and allocated to plant tissues with deleterious consequences for crop growth, yield as well as quality, and safety of production. Understanding of element biogeochemistry at the soil-microorganism-root interface, as well as the fate of elements in plants, is thus necessary to develop agronomic practices to minimize the supply of PTEs in soil, reduce their uptake by crops, and enhance plant strategies to cope with the problem. This chapter focuses on limitations in crop production caused by the occurrence of hazardous levels of copper (Cu), zinc (Zn), cadmium (Cd), arsenic (As), and chromium (Cr) in soil. The issue is addressed starting from the diffusion and forms of such elements in soil, moving to the mechanisms of plant acquisition and allocation, then to the effects on crops, and concluding with the agronomic strategies required to tackle the problem. Research fields to explore to find innovative and sustainable solutions to the problem are also reviewed.