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.
Humidity interacts most strongly with salinity effects.
This matters most in species with little ability to keep out toxic ions, such as chloride and sodium, that are carried with the vigorous transpiration stream caused by high humidity. Left in the leaves as the water evaporates, the ions accumulate, causing progressive leaf death and leaf drop. However, critical nutrient deficiency and toxicity levels are not established for many interesting plant species, analysis can be costly and slow, and there are straightforward, direct, and reliable methods the grower can do himself. Plant response trials are the ultimate test, and in hydroponic culture they can often give results within a few days. Run a comparison to see if the plants improve when you change the nutrient solution.