The effectiveness of foliar applied nutrition was first reported by the Michigan State University in the early 1950s. The U.S. Atomic Energy Department provided the University with a grant and radioisotopes of all nutrients for them to study the rates of absorption and movement within the plant. These early studies concluded that foliar applied nutrients were 8-10 times more effective in supplying the required nutrients than soil applied nutrients.
Other work has established the equivalency of foliar applied nutrients to soil applied nutrition. This type of work confirms what growers are seeing in their fields when foliar nutrition is used with a base fertilizer program.
The advantages of using foliar applied nutrition with a base fertility program are:
- Correct nutrient deficiencies as determined from soil or tissue tests
- Strengthen damaged crops
- Speeds up growth
- Stimulate root uptake
- Provide nutrient efficiency
Foliar nutrition results are highest when the plant is showing high growth activity, going from the vegetative to reproductive stage and when deficiencies are present or when the crop has been damaged. To achieve the best results, the foliar product should contain nitrogen to act as an electrolyte to carry the other nutrients and phosphorous to move the nutrients within the plant.
The foliar nutrients enter the plant through the leaf stomata and hydrophilic pores in the leaf cuticle. The nutrients are only absorbed while in solution on the leaf surface. For this reason, applications are best made in mornings and evenings when heavy dew is on the leaf surface, when there is high humidity, and temperatures are below 68°F.