application of fertilizers
can absorb a small amount of nutrients from dilute solutions sprayed
on to the leaves. Since the amount of micronutrients needed by
plants is very small, these can be supplied as foliar sprays,
especially if nutrients are chelated for better absorption. Plants
can also absorb macronutrients through the leaves, but it is not
possible to supply sufficient amounts this way; these must be taken
up by the roots.
application of macronutrients can help plants recover from temporary
stress due to moisture problems, pests or disease. Sprays containing
calcium can also be used to prevent blossom end rot in tomatoes and
other fruits, or tip burn in lettuce and cabbage which often occurs
during dry periods.