Ask your Agronomist: When to apply foliar fertiliser for best results

An agricultural extension official checks on tomatoes in a demonstration farm. In tomatoes, applying calcium as foliar may still result in incidences of blossom end rot despite having supplied the required calcium. PHOTO | JOSEPH KANYI | NATION MEDIA GROUP

What you need to know:

  • The efficiency with which the foliar-applied nutrients can be taken up and utilised by the crop will depend on the relative mobility of the particular nutrient.
  • In tomatoes for example, applying calcium as foliar may still result in incidences of blossom end rot despite having supplied the required calcium.
  • It is important to note that plants may suffer from certain nutrient deficiencies even though this may not physically be manifested yet.
  • For crop-specific fertiliser recommendations, please consult your Yara Agronomist near you or the Yara- accredited stockists and distributors in your area.

Q: Kindly comment on the use of foliar fertilisers, and also can I use only foliar fertiliser instead of the solid/granular ones?
Mutuku

Foliar fertilisers are indeed extensively used to supply plants with nutrients the world over.

In general, plants have the capacity to take up nutrients either through the leaf tissue or through the roots ( by diffusion, osmosis or interception by plant roots).

The principle route to use to supply the nutrients will depend largely on the relative amounts of the nutrients needed by the crop.

The efficiency with which the foliar-applied nutrients can be taken up and utilised by the crop will depend on the relative mobility of the particular nutrient.

The movement of these nutrients is mainly through the plants phloem tissue, through which they are conveyed to the sites where they are needed for optimum plant or cellular function.

So, for nutrients that are mobile within the plant, such as nitrogen and potassium, a foliar application would be okay in delivering them to the various plant parts.

However, for nutrients such as calcium, sulphur or iron that are very immobile in the plant, a foliar application will not be effective in delivering them to where they are most required.

In tomatoes for example, applying calcium as foliar may still result in incidences of blossom end rot despite having supplied the required calcium.

This is because the calcium will tend to be concentrated in the leaves and does not move into the fruits where its required to prevent the disease.

AMOUNT OF REQUIRED NUTRIENTS

Besides nutrient mobility, perhaps the most important consideration should be the amounts of the nutrients required by the crop.

The major plant nutrients – N, P, K – as well as the secondary nutrients Ca, Mg and S, are required in relatively large amounts by crops, such that a foliar route would not supply the needed amounts.

These nutrients must be supplied principally through the soil or other media for root uptake. Micro-nutrients on the other hand, including Zn, Cu, Fe and Mn are critical for plant production, but required in relatively low amounts.

These can, therefore, be efficiently applied through foliar fertilisers.

It is important to note that plants may suffer from certain nutrient deficiencies even though this may not physically be manifested yet.

This is especially so for the micro-nutrients compromising yields. Therefore, apply the micro-nutrients as a foliar to prevent full-blown deficiencies.

For effective use of the foliar products, use spreaders and stickers to ensure even application on the leaves and prevent the product from easily washing off the leaf surface.

For crop-specific fertiliser recommendations, please consult your Yara Agronomist near you or the Yara-accredited stockists and distributors in your area.

Vitalis Wafula
Yara East Africa Regional
Agronomist Contact us on: 0726 596050 or 0701669155