Evidence of lack or excess of certain minerals usually appears first in leaves but eventually affects
fruit size, quality, or yield. Leaves may be pale to white or yellow, having chlorotic blotches along
the veins or midribs. Leaves may also be mottled.
Maintain a good fertilization and irrigation program. Make sure you apply the appropriate fertilizer
at the right time. For oranges and grapefruit, apply nitrogen to the soil or foliage in late winter or
early spring; lemons may receive nitrogen at any time of the year. Foliar applications of potassium and
especially magnesium are most effective when the spring growth flush is two-thirds to three-fourths expanded.
A leaf analysis may reveal toxic levels of certain minerals such as sodium, boron, or sulfur. An excess
of these may be present in the soil naturally. Provide good soil drainage, and allow for extra irrigation
to wash the salts below the root zone. Deficiencies can be corrected with chelated foliar sprays.