Foliar fertilizer is a chemical or natural substance applied directly onto a plant’s leaves to improve its health and increase fertility.
Foliar nutrition stimulates root development

The total absorption capacity of the root system therefore increases. The plant will be able to absorb more water and nutrients because it reaches a larger volume of soil. As a result, the plant uses the reserves in the soil and the fertilizers more efficiently

Foliar fertilizers may be produced by the method of this invention containing as much as: 20% nitrogen, 25% phosphorous as P 2 O 5, or 25% potassium as K 2 O. Maximum content of primary nutrients is 32%.
The advantages of foliar fertilizers are increased yields and better disease resistance. Plants tolerate drought better and crop quality can be improved.

Because both stomata and leaf cuticle have evolved to help a plant limit the amount of water passing through them, foliar-applied nutrients need to be applied in the early morning or late afternoon, when the water they are dissolved in is less likely to evaporate quickly and stomata are more likely to be open.