Pierre Migner, retired agronomist, M.Sc., MBA / Literature review, August 2024 edition
Foliar fertilization consists of applying small, targeted amounts of nutrients or biostimulants directly to the leaves. It does not replace granular or soil-applied fertilization, but complements it by allowing a rapid intervention at strategic moments in the crop’s development.
This practice can help prevent or correct certain mineral deficiencies, support plants when soil conditions limit root uptake, and help crops through periods of stress such as cold, drought, excess water or salinity. It can also be used to support certain physiological processes related to flowering, fruiting, ripening and crop quality.
Foliar fertilization is a complementary, targeted intervention. Its effectiveness depends as much on the characteristics of the plant as on weather conditions, product formulation and spray quality.
Foliar fertilization makes it possible to supply nutrients at specific stages of vegetative development. It can be particularly useful when the roots are unable to efficiently absorb the nutrients present in the soil.
It can be used to:
However, the plant’s response varies depending on the crop, the nutrient applied, its stage of development and the conditions at the time of application.
The leaf surface is covered with a cuticle that limits water loss and protects the plant. Although this layer is naturally hydrophobic, nutrients can enter the leaf through different pathways, including hydrophilic pores, stomata and certain structures on the leaf surface.
The efficiency of this uptake depends on, among other things:
Small, soluble molecules with a suitable charge are generally easier to absorb. Chelating or complexing certain elements can also help improve their uptake and mobility in plant tissues.
Environmental conditions directly influence how long the solution remains available on the foliage.
According to the literature review, a foliar application should ideally be made:
Evaporation that is too rapid can cause nutrients to crystallize on the leaf surface and limit their uptake. Light dew can be beneficial, while rain or heavy dew can cause leaching.
Spray quality influences leaf coverage and the amount of nutrients that actually reach their target.
The review highlights the importance of nozzle selection, droplet diameter, the number of impact points and drying time. For a foliar fertilizer application, coverage of about 80 droplets per cm², with droplets 200 to 300 microns in diameter, is presented as an ideal target.
Adjuvants can also help reduce droplet bounce, improve spreading of the solution, prolong wetness on the foliage or facilitate the penetration of active ingredients. However, there is no universal adjuvant: each one must be chosen according to its function and the formulation used.
Agro-100 agro-liquids are formulated as solutions to promote their penetration into the foliage. They use small chelating agents and biostimulation technologies designed to support nutrient uptake and mobility as well as the plant’s response to abiotic stress.
Oligo Prime® technology is based on four complementary components:
A greenhouse trial on soybeans in 2021 evaluated the effect of C-plex® and FulviPro technologies on the uptake and mobility of calcium, manganese and boron. The reported results show higher average concentrations in the treatments with technologies than in those without, particularly for manganese and boron. To see these results, refer to the PDF at the end of this article.
Foliar fertilization is a precision tool that fits into a complete crop nutrition program. It allows a targeted intervention at key moments, particularly when the plant is under stress or when soil conditions temporarily limit nutrient uptake.
To maximize its effectiveness, it is essential to consider the crop, its stage of development, environmental conditions, the properties of the formulation and spray quality all at once.
