How are Visual Symptoms used as a diagnostic tool

Abstract

As a diagnostic tool, visual observation can be limited by various
factors including hidden hunger and pseudo deficiencies and soil or plant testing will be required to verify nutrient stress. Nutrient deficiencies and toxic ities cause crop health and productivity to decrease and may result in the appearances of unusual visual symptoms. General deficiency symptoms include stunted growth,
chlorosis inter-veinal chlorosis, purple or red discoloration and necrosis. Deficiencies of mobile nutrients first appear in older, lower leaves whereas deficiencies of immobile nutrients will occur in younger, upper leaves. Nutrient toxicity is most often the result of over application with symptoms including abnormal growth, chlorosis, leaf discoloration, and necrotic spotting.