Vol. 9, Issue 8, Part D (2023)

Nickel plays many important roles in the growth and development of plants. Its deficiency or toxicity symptoms can occur when it is present in too little or too much amount, respectively. Its status in soils is highly dependent on the nickel concentration of the parent rocks, but in surface soils, its content depends on soil-forming processes. Total Ni content in soils varied widely from 3.0 to 1000 mg kg^-1 and depends on the soil types. Total Ni content in soil positively correlates with the clay and organic matter content and negatively correlates with the fine sand content. Although it is present in various forms in soils, the most readily available form to plants is the Ni^-2+ ion. The availability of Ni depends on several physicochemical properties of soils. The magnitude of available Ni was reported to be higher in the lowlands than in the uplands. Its availability is greater in surface soils than in subsurface soils. High concentrations of Ni in plants adversely affect their growth and development. The toxicity levels of Ni vary widely and depend on plant species.