Toxicity of Micronutrients

A Narrow Safe Window

Because micronutrients are needed only in tiny amounts, the safe range between too little and too much is narrow: even a moderate fall in supply causes deficiency, while a moderate rise causes toxicity. A mineral ion's concentration in plant tissue is generally considered toxic once it cuts the tissue's dry weight by around 10%, though the exact critical concentration for toxicity differs a great deal between different micronutrients and between plant species — and toxicity symptoms in general are often hard to pin down precisely.

Excess of One Element Can Block Another …