Don't plants have to absorb nutrients through the roots?
Since the beginning, vegetative feeding has existed with all forms of plant life. In the early 1950's, scientists proved conclusively that plants could absorb minerals through their above ground parts. In general, they proved that 95 percent of the minerals applied to the above ground parts of the plant were absorbed into the plant. Only 10 percent of the minerals applied to the plants through the soil were absorbed.
Foliar feeding has existed with all forms of plant life. The marine algae and most other aquatic plants live in a one-phase water environment. The entire plant surface absorbs all the necessities of life, including minerals.
Leaf absorption research
As early as 1844, published reports demonstrated the use of the salts of various minerals as sprays for leaf feeding. In the early 1950's, Michigan State University scientists proved that plants could absorb minerals through their above ground parts. They used radioactive isotopes of the minerals and tracked them with a Geiger counter.
The idea that plants absorb nutrients through their roots is commonly accepted. Nutrient transportation then occurs to other portions of the plant. MSU researchers Bukovac, Teubner, Tuky and Wittwer proved that the reverse of this process also occurs: there is an uptake of nutrients through the stems, leaves, flowers, and fruits of plants.
These Michigan State University researchers stated that minerals are absorbed by the above ground plant parts and move rather freely in the plant. The amounts absorbed may seem rather small, but to offset that problem, the efficiency is very high. In general, they proved that 95 percent of the minerals applied to the above ground parts of the plant were absorbed into the plant. While plants absorbed only 10 percent of the minerals applied to them through the soil.