Proper plant nutrition is one of the main factors for high crop productivity, since balanced nutrient replenishment is essential to maintain the physiological capacity of plants (Saldanha et al., 2016). However, at certain stages of development or under certain soil conditions, root absorption may be limited. An example is the use of phosphorus in acidic soils, where a large portion of the applied phosphorus remains unavailable to plants (Pavinato et al., 2020).

In these situations, foliar nutrient application is a complementary alternative. Foliar fertilization is based on the ability of leaves, although specialized in photosynthesis, to absorb water and nutrients (Saldanha et al., 2016). This technique allows for the targeted supply of macro and, mainly, micronutrients. Therefore, it is used in various crops to correct specific deficiencies and in specific organs, such as the direct supply of calcium (immobile in the plant body) to the fruits in apples and tomatoes (Saldanha et al., 2016). It also stands out for improving the efficiency and utilization of fertilizers, enabling applications at later stages of the cycle, and promoting plant growth and development.

However, the efficiency of foliar fertilization depends on a series of internal and external factors that affect the absorption and translocation of nutrients in plants (Faquin, 2005). Foliar absorption is necessarily via the cuticle (Saldanha et al., 2016). Although it was thought that the cuticle was a continuous and impermeable layer, it is now known that it has microchannels and discontinuities that allow the passage of solutes. The thickness of the cuticle, the presence of stomata, trichomes, and the hydration of the leaf itself directly influence absorption.

Young leaves, due to their thinner cuticles and higher metabolic activity, tend to absorb nutrients better than older leaves. Furthermore, the lower (abaxial) surface of the leaves, generally richer in stomata and with less wax deposition, is usually more efficient at absorption. Therefore, uniform spraying is crucial when applying foliar fertilizers, aiming to reach both sides of the leaf (Faquin, 2005).

Environmental conditions at the time of application are also crucial. Relative air humidity and temperature influence the drying time of the spray solution on the leaf surface. High temperatures and low humidity promote rapid evaporation of the solution, hindering the formation of a liquid film necessary for absorption. Therefore, applications should preferably be carried out in the early morning or late afternoon, when the leaves are hydrated and the stomata are open (Faquin, 2005). The presence of light is also an important factor, as it stimulates stomatal opening and activates metabolic processes that provide energy for the active transport of nutrients.

Another important point concerns the mobility of nutrients in the phloem. Elements such as nitrogen, phosphorus, and potassium are considered mobile and, therefore, are easily redistributed to other parts of the plant after absorption (Faquin, 2005). Nutrients such as calcium and boron, on the other hand, have low mobility and remain at the application site, requiring frequent and well-targeted spraying of the target tissues.

The composition of the applied solution also affects efficiency. The chemical form of the nutrient can increase or decrease its absorption rate. Urea, for example, exhibits a high rate of leaf penetration and also promotes increased cuticular permeability, which favors the absorption of other ions present in the solution. This occurs because urea is able to break chemical bonds between the components of the leaf cuticle (Saldanha et al., 2016). However, at high concentrations it can cause phytotoxicity.

The use of amino acids with a complexing effect alongside minerals can promote greater membrane penetration and faster absorption compared to free ions, increasing the efficiency of foliar fertilization (Lambais, 2011; Marques, 2014). This is the case with ILSAMIN Agile, composed exclusively of amino acids from the organic matrix GELAMIN, a natural source of rapidly absorbed amino acids. Other solutions developed by ILSA combine GELAMIN amino acids with mineral sources of macro and micronutrients. An example is ETIXAMIN MEGA, an organomineral fertilizer that, in addition to amino acids from GELAMIN, contains nitrogen, boron, zinc, manganese, phosphorus, potassium, molybdenum, sulfur, copper, and magnesium, favoring their absorption.

Regarding the timing of application, foliar fertilization is generally carried out during periods of greatest crop demand, when deficiency symptoms usually appear. However, this form of fertilization is also used for nitrogen in coffee seedlings and for boron and molybdenum in seedlings in vegetable seedbeds, for example. ETIXAMIN KALLY is an organomineral fertilizer exclusive to ILSA, formulated as a water-soluble powder containing enzymatically hydrolyzed proteins (a natural source of organic N and rapidly absorbed amino acids), along with nitrogen, potassium, and sulfur of mineral origin. In soybean cultivation, potassium (K) and sulfur (S) are absorbed significantly up to stages close to R5.5 (EMBRAPA, 2025). Therefore, this phase still represents a strategic moment to correct any deficiencies of these nutrients, ensuring their utilization by the plant before the end of relevant absorption.

In addition to the direct effects on plant growth, studies show that foliar fertilization can increase the efficiency of fungicides, reduce disease severity, and contribute to higher productivity. In wheat, for example, synergism has been observed between foliar fertilizers and pesticides, with a positive impact on productivity (Marques, 2014). Well-nourished plants are more resistant. Furthermore, from an operational point of view, the combination of these practices is also advantageous.

Although foliar fertilization offers a number of benefits, it requires careful consideration. Its rational use demands technical knowledge of the crop's nutritional requirements, the plant's stage of development, and environmental conditions. Because it leaves no residual effects in the soil, several applications are usually necessary throughout the cycle. Even so, the required doses are lower, and absorption is faster, provided conditions are adequate. Therefore, when well-planned and executed, this practice represents a tool to maximize productivity and promote crop health.

Bibliographic references

EMBRAPA. PHENOLOGICAL STAGES AND NUTRIENT ABSORPTION PATTERN OF SOYBEAN. Accessed in: August/2025. Available at: https://www.embrapa.br/busca-de-publicacoes/-/publicacao/1047123/estadios-fenologicos-e-marcha-de-absorcao-de-nutrientes-da-soja.

FAQUIN, V. Mineral nutrition of plants. Postgraduate Course “Lato Sensu” (Specialization) Distance Learning: Soils and Environment. Lavras: UFLA/FAEPE. 2005. 186 p.

LAMBAIS, GR. Amino acids as adjuvants to foliar fertilization and the use of glyphosate in soybean cultivation. 2011. 97 p. Dissertation (Master's) – Postgraduate Program in Sciences, Luiz de Queiroz Higher School of Agriculture.

MARQUES, LN. Foliar fertilizer in association with fungicide in wheat. 2014. 120 p. Dissertation (Master's) – Postgraduate Program in Agronomy, Federal University of Santa Maria.

SALDANHA, CB et al. Soil Science: Soil Fertility and Mineral Nutrition of Plants. Londrina: Editora e Distribuidora Educacional. 2016. 192 p.

PAVINATO, PS et al. Revealing soil legacy phosphorus to promote sustainable agriculture in Brazil. Scientific Reports, v.10, n.1, 2020.

Authors

Agr Eng. MSc. Isabela Bulegon Pilecco
Agricultural Eng. Msc. Thiago Stella de Freitas
Agricultural Engineer Tuíra Barcellos