The following are examples. The high levels of calcium supplied in most culture solutions help protect against these factors. Alkalinity forces zinc and especially iron out of solution, often leading to severe deficiencies of these metals despite the use of chelating agents to help keep them in solution. Interactions involving Phosphorus Most hydroponic media formulations supply dissolved phosphate concentrations at least 100 times higher than soils do. Recent studies indicate that high phosphate concentrations can cause phosphorus toxicity in several kinds of plants, especially if iron and calcium nutrition is not ideal, or if nitrate is kept at low levels.
High phosphate can also aggravate salt damage and zinc deficiency.
Judicious reduction of phosphate levels in hydroponics may turn out to be an appropriate modification for many kinds of plants. Salt damage in chickpea aggravated by low relative humidity. Interactions involving light and humidity Light intensity influences the expression of symptoms of some deficiencies and toxicities. For example, growth at low light intensities suppresses the development of symptoms of zinc deficiency and phosphate toxicity. More important, when increasing light improves growth it also increases the nutrient demand and the likelihood of all deficiencies.