Foliar nutrition: correct timing & application

Why foliar fertilization?

Foliar fertilization may still seem like a relatively new phenomenon, but did you know that more than three centuries ago it was already discovered that plants can absorb water and nutrients through their leaves? And that foliar fertilization has been used in agriculture since the early 19th century?

There are several reasons to apply foliar fertilization in horticulture and arable farming. These are the most important:

• Quickly correcting a nutrient deficiency during cultivation: foliar fertilization usually works within one week, minimizing yield and quality losses.
• Supplying nutrients when uptake through the soil is reduced: trace elements such as manganese are difficult for plants to absorb at a soil pH higher than 6.2 (Handbook Soil & Fertilization). Foliar fertilization can still meet the crop’s manganese requirements in such situations.
• Protecting and feeding the crop in a single application: in some cases, foliar fertilizers can be combined with a crop protection spray. Always check beforehand whether the desired tank mix is physically compatible.
• Optimally feeding the crop within legal application limits: due to restrictions on the maximum amounts of nitrogen, phosphate, and animal manure, it is not always possible to fully meet the crop’s nutrient requirements through base fertilization alone. Supplementing the base fertilization with efficient foliar fertilizers can still make high yields possible.

Important conditions

The effectiveness of foliar fertilizers differs greatly between plant species and depends on several factors:

Plant characteristics

Each plant species has its own characteristics. Plants with water-repellent leaves (such as various cabbage species) or a thick wax layer absorb water and nutrients less easily (Fernandez, 2013). The plant growth stage is also important. Most plants absorb nutrients most effectively during the exponential growth phase (Alexander, 1986).

Weather conditions

Plants absorb foliar fertilizers best when the spray solution does not dry too quickly on the leaf surface. Therefore, spray during periods of high relative humidity, mild temperatures, little sunlight, and low wind conditions (WUR, 1994). Preferred application times are early morning or late evening.

Quality of the foliar fertilizer

Complexed foliar fertilizers are more stable (remain better dissolved) and are therefore more easily absorbed than fertilizers containing only the active nutrient (Alexander, 2016). Soiltech’s Optima Leaf foliar fertilizers are organically complexed, have very high uptake efficiency, are gentle on the crop, and are easy to combine in tank mixes. When selecting a product, pay attention not only to the cost but also to the formulation.

Method of application

Foliar fertilizers are often applied using a conventional field sprayer. Spraying with fine droplets provides the best leaf coverage, but this may not always comply with drift reduction regulations. Take this into account when selecting spray nozzles.

Risks

Applying foliar fertilizers is not always without risks. Leaf scorch is one of the most common consequences of incorrect use. Scorching is usually caused by excessive dosage or overly rapid drying of the foliar fertilizer. In addition, physical compatibility may also be an issue. Not all foliar fertilizers can be combined with other products. Always follow the application instructions regarding physical compatibility or consult your supplier.

Complexed foliar fertilizers

Soiltech offers a wide range of liquid foliar fertilizers under the name Optima Leaf. These foliar fertilizers are organically complexed, meaning the active nutrient (for example manganese or copper) is bound to an organic molecule.

An organically complexed fertilizer offers several advantages compared to non-complexed or chemically complexed fertilizers:

• The fertilizer is gentler on the crop and carries a lower risk of leaf scorch.
• The active nutrient is more easily absorbed through the leaves.
• The fertilizer is more stable and better compatible with other products in tank mixes.

Research

Soiltech’s R&D department is equipped with a professional trial greenhouse in which the safety and efficiency of the foliar fertilizers are extensively tested. An automated spraying system allows for highly accurate dosing. The safety of foliar fertilizers is tested in the greenhouse on crops such as radish and beans, as these crops are sensitive to scorching. After extensive greenhouse screening, field trials are conducted under practical cultivation conditions.

Would you like to know more about the compatibility of Optima (foliar) fertilizers, biostimulants, and adjuvants? Click here!