Lehtilannoitus

Lehtilannoitus, or foliar fertilization, is the agricultural practice of applying nutrient solutions directly to plant leaves. The aim is to supply essential elements quickly and locally, often to correct deficiencies or to supplement soil-available nutrients.

The practice is commonly used to address micronutrient deficiencies (such as iron, zinc, manganese, copper, boron) and to provide rapid nutrition when soil conditions limit root uptake. It is particularly useful in high-pert crop production, in greenhouses, or when soil pH, salinity, or drought reduce nutrient availability. Foliar feeding may also be employed to complement soil fertilization and to improve crop quality or stress tolerance.

Nutrients applied foliarly are usually in dilute solutions and may include nitrogen, phosphorus, potassium, as well as micronutrients. Macronutrients are used more selectively due to the risk of leaf damage and higher costs. Applications are typically made with sprayers that ensure even leaf coverage, often during cooler parts of the day to minimize evaporation and leaf burn. Adjuvants or surfactants are commonly added to improve leaf surface wetting and uptake.

Advantages of lehtilannoitus include rapid nutrient uptake, targeted correction of deficiencies, and usefulness when soil conditions impede root absorption. Limitations include the potential for leaf burn from concentrated solutions, salt injury, interactions with pesticides, and the fact that foliar feeding cannot fully replace soil-based nutrition. Effectiveness depends on species, growth stage, weather, leaf area, and proper formulation and timing of the application.