Foliar fertilization means the spray application of nutrients to the plant leaves and stems and their absorption.
The observed effects of foliar fertilization include yield increases, better resistance to diseases and pests, improved drought tolerance, and enhanced crop quality The plant’s response is dependent on species, fertilizer form, concentration, and frequency of application, as well as the stage of plant growth. Foliar applications are often timed to coincide with specific vegetative or fruiting stages of growth, and the fertilizer formula is adjusted accordingly. The amount of nutrients that plants can absorb via foliar application is limited, and generally much less than their total nutrient requirements.
Foliar application should therefore be used as a supplementary form of fertilization. It cannot replace basal fertilization.
Foliar fertilization should not be considered a substitute for a good soil-fertilization programme
Recommendations for efficient foliar application:
- The best times for foliar spraying are early morning and late afternoon, when humidity is higher and the leaves are in a state of full turgor, with their cells full of water.
- Avoid foliar spraying during the warmer hours of the day; absorption at high temperatures is very poor
- and plants may be exposed to stress and suffer scorching.
- Dew formation after foliar application is an important aid to prolonged penetration, because of resolubilization of the fertilizers in the dew collected on the leaves.
- Spraying should take place under minimal wind conditions. This is especially important with finely atomized sprays, as they drift readily.
- Always spray when soil moisture is sufficient. Leaves will then be turgid and not susceptible to water stress. Consider irrigating on the day prior to spraying.
- Avoid foliar spraying just before rainfall or overhead irrigation in order to prevent the sprayed materialbeing washed off.
- The optimum pH for a foliar spray is slightly acidic (5 ± 0.5).
- The use of a suitable wetting agent or surfactant decreases the surface tension of the spray droplets,
- which improves the distribution of the droplets, increases the wetted surface area, reduces burning/ scorching of the leaves, and improves the uptake of the product. Always check the compatibility of the surfactant with the foliar fertilizer.
- Ensure that the fertilizer is fully soluble. No special equipment is required – foliar solutions can be
- applied with the aid of conventional spray equipment, e.g. a fan sprayer, a backpack sprayer, a sleeve
- sprayer, an aerial sprayer, etc.
- Select the appropriate sprayer volume and pressure for each crop. Using the correct volume of spray is essential to achieve full coverage of the plant canopy.