Diagnosis of micronutrient deficiencies and evaluation of their severity are a prerequisite for their correction. Early studies on plant nutrition were, therefore, concentrated on development of methods for diagnosis of micronutrient deficiencies. Pioneering contributions in this regard have been made by Wallace (1961), Sprague (1964) and Chapman (1966). The methods for diagnosis of micronutrient deficiencies are essentially based on the following: a. Foliar symptoms b. Plant analysis c. Soil tests d. Biochemicu. and spectral changes e. Crop response to fertilizer amendment
Judicious and sustainable management of deficiency of a micronutrient requires a quantitative assessment of its availability to plants. This is critical for correction of deficiency through fertilizer amendments. The dose of micronutrient amendment has to be chosen in such a way that it raises the availability of the applied micronutrient to give optimal yields but does not build its concentration to a toxic level. It, thus, becomes imperative to not only identify the limiting nutrient but evaluate the severity of its deficiency which determines crop responsiveness to fertilizer application.