Foliar fertilization is used to ensure optimal crop performance when nutrient supply from the soil is inadequate or uncertain. Foliar fertilizers (foliars) offer specific advantages over soil fertilizers when:
- Plant demand for nutrients exceeds the capacity for root nutrient uptake;
- Elemental mobility within the plant limits delivery to tissues and
- Environmental conditions limit the effectiveness or prevent the application of nutrients to the soil.
However, foliars cannot replace soil-applied fertilizers. It is supplemental, but often the reaction to foliars are more than the sum of nutrients applied.
Demand: Foliar fertilization is applicable if any of the following situations prevail:
- Plant demand exceeds the capacity of the root to absorb the nutrient. This occurs when:
- Soil conditions limit nutrient solubility or delivery to the root as a consequence of unfavorable pH or chemical composition of the nutrient; excess soil concentrations of competing ions; unfavorable conditions for root growth; or soil environmental conditions that limit nutrient uptake (unfavorable temperature, moisture or oxygen content).
- A limitation in uptake capacity due to plant phenology, such as during early spring when many deciduous species flower and set fruit during periods of unfavourable soil temperatures.
- During periods of peak nutrient requirement such as rapid fruit growth when demand for nutrients can exceed the ability of roots to supply adequate nutrients even in a well-fertilized soil. This make the application timing of foliar fertilizers very important. It should not be a “shotgun” approach.
- When localized within-plant demand exceeds the capacity for within-plant nutrient re-distribution.
- This commonly occurs near large fruit and nut clusters, or during grain fill or storage tissue development, and is related to both the highly localized demand for elements (notably N and K) or because of low phloem mobility of certain elements (notably Ca and B). Again, application timing is crucial.
- Within-plant element mobility can also be limited if flowering precedes leaf expansion and thereby limits xylem nutrient transport.
- Periods of drought or high humidity can also limit both xylem flow as well as restrict the delivery of phloem-immobile nutrients.
- When plant demand cannot be satisfied and soil application is prevented due to:
- Field conditions (such as wet fields etc.),
- application costs or
- growth stage of the crop.
Supply: the efficacy of foliar fertilization is determined by:
- The physical and chemical characteristics of the fertilizer, which determines the total quantity of nutrient that can be delivered and the compatibility of that nutrient with other chemicals.
- The use of additives (surfactants, humectants, spreader/stickers, etc.) and the method of application.
- The environment at the time of, and following, foliar application.
- The ability of the nutrient to penetrate into the cytoplasmic volume which is influenced by species; leaf type and age; chemical characteristics of the fertilizer; environmental conditions; and application method.
- The mobility of the applied nutrient within the leaf that is determined by its relative phloem mobility, species characteristics, leaf age and immobilization of the element at the site of application.
The factors that determine the efficacy of foliar fertilization are complex and encompass aspects of physics, chemistry, environment, biology and economics as well as intangibles such as risk aversion and ease of management. Therefore, the decision to use foliar fertilizers requires consideration of each of these demand and supply factors balanced against the relative costs. If foliar fertilization is mixed with post emergence herbicides, insecticides, or fungicides, the probability of yield response could be increased and cost of application can be reduced1.
In circumstances where the soil-type, cropping system or the environment prevent or limit soil application or nutrient withdrawal from the soil of the required nutrients then foliar fertilization represents an essential practice and therefore the primary challenge is to apply foliar formulations and use application methods that are as efficacious and economical as possible. To prevent inefficient use of foliar fertilizers it is important that growers know when and why to apply it.
Foliar fertilization, as currently practiced, is both a science and an art. For the science of foliar fertilization to be optimized there is a substantial need to understand the factors that govern the efficacy of foliar fertilizers and to apply formulations and use application methods that maximize the chance of beneficial response.
Adapted from: Foliar Fertilization: Scientific Principles and Field Practices, V. Fernández, T. Sotiropoulos and P. Brown. 2013. International Fertilizer Industry Association; firstname.lastname@example.org, www.fertilizer.org. 1Foliar Fertilization of Crop Plants, N. Fageria; M. B. Filho; A. Moreira and C. Guimar, Journal of Plant Nutrition, 2009, Vol. 32, pp. 1044 – 1064.
Which Foliar Fertilizer?
Various water soluble fertilizers can be used for aerial application. These products can increase some nutrients in the plant and give the plants a boost, especially under waterlogged situations where the plant roots cannot absorb any nutrients from the soil. They are usually not sufficient to address micronutrient deficiencies, but together with specific products can have an exponential effect on plant growth. COMPO EXPERT’s range of water-soluble fertilizers with stabilised nitrogen, Novatec® Solub is ideal.
Nutrimix® Complete and Nutribor® from COMPO EXPERT are new generation fertilizers designed to correct and prevent deficiencies in extensive crops (wheat, maize, canola, cotton) and tree crops (olive, citrus and other fruit). The completely soluble and highly available elements include nitrogen (N) magnesium (Mg), manganese (Mn) and zinc (Zn), which strongly stimulate photosynthetic activity in plants, and boron (B), copper (Cu) and iron (Fe), which improve fruit set and pollen fertility.
Designed for foliar applications, they have important characteristics that maximize their effectiveness and superior performance such as:
- High purity
- High solubility
- High absorption capacity and translocation within plant tissues due to chelation.
Numerous studies have shown the foliar application of micronutrients on wheat increased tillering ability, spike length, grain yield and the quality of the wheat. You can apply micronutrients as a foliar application with Nutrimix® Complete.
Nutrimix® Complete Results
For boron demanding crops (oil crops like canola, sugar beets, cotton, etc.) and boron deficient growing conditions (sandy soils, high pH, etc.) use Nutribor®.