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The Ultimate Guide to Foliar Fertilizer

Maximize plant growth with foliar fertilization: a guide on benefits, application techniques, and best practices for optimal nutrient absorption.

Plants take up nutrients more quickly through leaves than from the soil. Under some circumstances (low soil fertility), when plants can’t easily take up nutrients through the soil, farmers resort to spreading fertilizer on the surface of leaves. This process is called foliar fertilization.

The main goal of foliar fertilization is balancing their nutrient profile and allowing plants to take up essential nutrients necessary for their overall growth. Using this type of fertilization can lead to improved yield in some cases.

In this article, we are going to talk about everything regarding foliar fertilizer, right from its process and benefits to its viable application techniques. 

How do Foliar Fertilizers Work?

The working mechanisms of foliar fertilizer can be better understood once you know the structure of a leaf. 

The entire leaf is surrounded by the epidermis layer, which acts as a barrier between plants and their external environment. It mainly absorbs water and nutrients from the outside and protects against water loss. The small openings in the epidermis that regulate water and gasses help foliar feeding to reach the core.

Once the fertilizer is applied on the surface of the leaves, the stomata act as a semi-permeable passage. Through these openings on the leaf’s surface, the macronutrients get absorbed in the plant’s vascular system.

And then these macronutrients transported here are then utilized for various purposes related to plant growth, such as photosynthesis aiding in plant growth.

Benefits of Foliar Fertilizers

There are several benefits associated with the right usage of foliar feeding or applications. Here are some of them:

Increased Pest Resistance 

With the quick and accurate dosage of essential nutrients like N-P-K, boron, and silicon, the production of defense-related compounds like phytoalexins is increased. It primes the plants to respond to exposure to certain stimuli by activating defense mechanisms in the right way.

Additionally, it reinforces the cell wall that prevents pest feeding. In some cases, they even promote the growth of beneficial organisms that prey on pests. 

Improved Nutrient Uptake

Improved Nutrient Uptake

As the absorption occurs at the surface level, the liquid can easily penetrate the plant. And because of the easy pathways, the soil-related issues are eliminated easily and the flower’s overall growth is supported. 

For instance, the Nitrogen (N) boost initiates auxin regulation that helps plants elongate. Foliar-applied K (Phosphorus) ensures that turgor pressure is maintained properly in the plant, ensuring proper growth.

Reduced Dependence on Soil Fertilization

By foliar application, nutrient mobility increases by a greater factor than soil. Therefore, this kind of fertilization serves as an alternative to soil fertilization, and the dependence on traditional fertilization methods is greatly reduced.

This could be a great solution for agricultural settings where conditions like water logging occur quite frequently.

Potential Improved Yields

The bio-stimulants in the fertilizers give the necessary hormonal signals to the plants during the growth or fruiting season. This could potentially lead to improved yield, especially in terms of quality.

In addition to the above, the growth stimulants also help in mitigating plant stress during drought and extremely hot weather. At the end of the day, when plants are able to withstand environmental stress, the fruits with better texture, flavor and firmness are more likely to grow. 

Types of Foliar Fertilizers

Based on the application and composition of foliar fertilizers, they can be classified into different types. Let us take a look at some of them one by one:

Organic Foliar Fertilizers 

Organic foliar fertilizers are made from seaweed or fish emulsions. These kinds of fertilizers are rich in amino acids and growth hormones. Therefore, they are specifically used to support root development and increase stress tolerance. 

Macro-Nutrient Fertilizers

These are the most commonly used foliar fertilizers that contain nitrogen, phosphorus, and potassium in a controlled composition. Such kinds of fertilizers are used to promote vegetative growth. These foliar applications are used to treat plant-related diseases such as zinc deficiency and iron chlorosis.   

Micro-Nutrient Fertilizers 

They contain traces of elements like Fe (Iron), Zn (Zinc), Cl (Chlorine), and Mo (Molybdenum). Plants require them in a lesser form than the N, P, and K. The foliar application for these is more common in cases of crops with precise nutrient demands. 

Chelated Foliar Fertilizers

The foliar applications of chelated fertilizers ensure that both macro and micro nutrients bind with ligands to form water-stable compounds. With its application, fast nutrient correction can be ensured. 

In addition to the above, it can reduce the probability of phototoxicity risk. Its applications vary from field, fruit, vegetable, and oilseed crops. 

When to Apply Foliar Fertilizers?

Though the foliar application has many benefits, it’s still not the perfect solution in every case you see. Here are some specific cases where using such a fertilization can reap good results. 

During Nutrient Deficiency

Nutrient Deficiency

In these times when plants struggle to take up essential nutrients from the soil, having a foliar application would be better. 

Because of the quick absorption, the macronutrients will effectively be transported to the right place, leading to quick recovery from conditions like improved stress and drought. 

If you find your leaves turning pale yellow or white, it is a sign that they need Fe (Iron); hence, an application would be a good option to consider. 

Before Fruition Stages  

Before and during the growing stage is when a plant needs most of the nutrients. With an adequate amount of N, P, and K in the vascular system, the plants will be able to do their activities like photosynthesis. It will also prepare them for the fruiting stages. This may also lead to better fruition and expansion of the plant.

In the case of tomatoes and berries, a regulated P or K boost in the soil profile could produce quality yield. However, foliar application during the time of fruition is not recommended, therefore it must only be done before that stage. 

Cool Temperature 

In cool temperatures, the metabolic activities of a plant decrease by a factor. In such a case, foliar fertilization would be helpful. Note that the cooler temperature greatly favors foliar fertilization. 

Therefore, if you live in a colder region, this may be a good option to consider. However, it is important to note that the application depends on the type of crop you are growing. 

Specialized Nutrient Requirements

Specialized Nutrient Requirements

A few crops, such as citrus and tomatoes, have very precise nutrient requirements. By foliar feeding, you can ensure a precise application of fertilizers. For example, citrus trees are susceptible to conditions like iron chlorosis. 

To address this issue, a fertilizer application in soil may take a longer time, compromising the fruit’s quality. But regular foliar applications of chelated iron can save the day. 

What Kinds of Plants Need Foliar Fertilization?  

Not every plant would benefit from fertilization. Therefore, it is necessary to understand the plants that could benefit from foliar fertilization. Let us understand this with the help of a table.

Plants that Benefit from 

Foliar Fertilization

Plants that Typically Do Not Benefit from 

Foliar Fertilization

Fruit-bearing trees as well as Shrubs (e.g., Citrus, apple)

Deep-rooted crops with extensive root systems (e.g., corn, wheat)

Vegetables (e.g., tomatoes and peppers)

Crops with thick, waxy, or hairy leaves that inhibit nutrient absorption (e.g., cabbage, kale)

Flowering plants (e.g., roses, orchids)

Plants grown in well-fertilized soils with balanced nutrient levels.

Indoor houseplants (e.g., ficus, Peace Lily)

Hydroponically grown plants receive nutrients directly through the water solution.

Container-grown plants (e.g., potted herbs)

Aquatic plants primarily absorb nutrients through their roots from the surrounding water.

It is important to note that foliar application must be strictly considered for a certain kind of plant. 

How to Apply Foliar Fertilizer?

For foliar application, two ways are quite commonly used. One of them is by using a hose-end applicator and the other one is by applying a sprayer. As the liquid is not equally distributed using the hose-end applicator, the sprayer should be used to ensure that the leaves are covered properly.

Here’s a step-by-step guide on how you can spray a foliar fertilizer. 

  • Make sure that the spraying equipment, such as the backpack and hand sprayer, is clean.
  • Assess if the leaves are clean or not. Any debris or dirt may hinder the proper absorption of the fertilizer through the epidermis.  
  • Calibrate the sprayer to ensure that the right amounts of fertilizer are sprayed.
  • Dilute your foliar fertilizer in the spray tank. The dilution percentage should be according to the fertilizer’s diluting instructions.
  • Then, mix the fertilizer thoroughly with the water. 
  • Take out any debris, weed, or any solid particles in the mixture that may cause problems in application. 
  • If you have other plants nearby that don’t need fertilization, cover them with plastic sheets. 
  • Spray the fertilizer, making your way from bottom to top and covering each part of the leaves. Go for a sweeping motion to ensure all the sides of the leave receive an equal amount of foliar feed. 
  • Keep applying the solution until the fertilizer starts to drip from the surface of the leaves. 

Monitoring and Follow-Up

  • After a few minutes, carefully observe whether a part of the plant needs to be fertilized or not. Redo the application on those leaves. 
  • Once the application is complete, clean the equipment with water until the liquid is no longer there. 
  • In case you want to save the fertilizer for usage in future, keep it in a sealed container in a dry place, away from sun rays.
  • Check the leaf’s condition properly, in case it becomes pale yellow or white, and change the concentration of fertilizer accordingly. 

What to be Considered While Foliar Fertilization?

Let us review some additional tips to be considered during foliar fertilization. 

  • Don’t apply foliar fertilizer during the hot weather and extreme summers; it may cause leaf burns. 
  • Keep a proper check on the weather; if you forecast any signs of rain in sight, delay your foliar application. 
  • Always apply fertilizer in a balanced quantity. Overapplication of foliar fertilization could lead to some consequences like leaf burns
  • While applying the fertilizer, make sure the pressure levels are adequate and only produce small droplets of liquid. 
  • Apply the fertilizers early in the morning or late afternoon to get the best results. 

When Not To Do the Foliar Feeding?

Now that we know the application techniques and the ideal scenarios for applying foliar fertilization, it’s equally important to know when it shouldn’t be considered. Don’t go for foliar feeding if you are dealing with:

Sensitive Plants 

Nutrient requirements usually vary from one plant to another. The sensitive plants may not be able to cope with a boost of macro and micronutrients. If fertilization is necessary, go for a fertilization test on some part before covering the whole of it. 

New Seedlings

New Seedlings

In the very initial stages, plants have a very under established root system. This may not be good for the delicate root system. Giving the plants a nutrient feed in such situations is not ideal. It is wise to wait until the seedlings grow. 

For instance, if you want to fertilize tomato seedlings, look for signs such as stem thickness and leaf color. 

Nutrient-Rich Soil

If the soil is already rich in nutrients, the foliar application is unnecessary. In some cases, it may even cause nutrient imbalance, while in others, it may lead to consequences such as salt buildup or stunted growth. 

Parting Comments 

It can be concluded that, in some cases, foliar fertilizing can be an excellent choice for fertilization. However, it is not a replacement for soil fertilization. This could lead to better growth, high yields, and even better quality crops. The only condition is that the right amount of fertilizer should be applied at the right time. 

While applying the fertilizer on the leaves, always cross-check that the entire leaf has equal application. In addition to this, always consider the best practices mentioned above in the process of fertilization. 

Last but not least, always take a soil test before you choose foliar fertilization to mitigate the risk of nutrient excess. To improve yield or get fertilizers-related advice, always consult an expert who could guide you in the process. 

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