What is 18-18-18 Fertilizer Used For? | Best Guide

If you want to know, what is 18-18-18 fertilizer used for, you will love this in-depth guide.

Now you might be wondering, what does this number show?

This number is the NPK ratio. In simple words, it tells the percentage of 3 elements in the fertilizer. These three elements are Nitrogen, Phosphorus and Potassium.

So here’s what the triple 18 fertilizer contains:

  • Nitrogen: 18%
  • Phosphorus: 18%
  • Potassium: 18%

And other nutrients as well.

Before talking about this fertilizer, let me introduce these nutrients to you.

What Does “18-18-18” Mean?

As I mentioned above, this number shows the percentage of three elements:

  1. Nitrogen.

Nitrogen is an extremely important nutrient for plant growth.

Here’s why.

It is a source of energy for metabolic reactions. In plants, metabolic reactions include photosynthesis, nitrogen fixation and respiration.

Plus, it leads to good leaf growth in plants. Can you guess why this is so?

Nitrogen is used to make amino acids, proteins, DNA, and nucleic acid. You should know that a plant cannot grow properly without amino acids.

Now let me tell you how a plant absorbs Nitrogen.

Note that a plant cannot take up Nitrogen directly from the soil. It is obtained when ammonia is added to the soil, and the plant takes up nitrogen in the form of NH₄⁺ and NO₃⁻ ions.

18-18-18 fertilizer

Plants get Nitrogen in the form of nitrates as well. This is possible due to animal wastes and dead bacteria present in the soil.

Now let’s talk about Phosphorus in the triple 18 fertilizer.

  1. Phosphorus.

Phosphorus is an important component of ATP (Adenosine triphosphate). Now you might be wondering, what is ATP.

It is a structure that provides energy to the plant.

This nutrient is important in the normal growth and metabolism of plants. The major function of Phosphorus is that it supports the root and shoot system of plants.

Moreover, it leads to flower and fruit development as well. Now you might be wondering, how does a plant obtain phosphorus?

A plant takes up phosphorus in its primary forms. These are called orthophosphates, H2PO4 and HPO42-.

This happens due to diffusion (movement of substances from higher concentration to lower concentration).

Note: Phosphorus is usually taken up by the plant when the soil pH is less than 7.0.

Now let me introduce potassium to you.

  1. Potassium.

As I mentioned above, this fertilizer has 18% potassium. Here’s why it is important.

It is used for the growth and development of the plant. Potassium is used by plants for the movement of water, carbohydrates, and nutrients.

It is also used to activate the enzymes which make ATP, starch, and proteins. Note that enzymes are biological catalysts that speed up a reaction.

You should know that it regulates the opening and closing of stomata as well.

For your knowledge, let me tell you that it is taken up by the plant in the form of potassium ion (K+).

The best part is that it quickly dissolves in water. So it is obtained when the plant absorbs water from the soil.

Pretty simple, isn’t it?

Now let’s jump straight to our next topic.

What is 18-18-18 Fertilizer Used For?

Here are some of the benefits of using this fertilizer:

  • It is water-soluble.

Here’s why this is important.

Nutrient levels are not affected by leaching and erosion. Note that leaching is the loss of soluble substances from the top layer of soil.

what is 18-18-18 fertilizer used for?

The best part is that the nutrients are easily available for absorption by plants. Plus they are easy to apply through fertigation.

Note: Fertigation is a process in which the fertilizer is included within the irrigation water. This drip-irrigation system makes this fertilizer application method effective.

  • The macronutrients present lead to healthy plant growth.

For your reference, let me tell you that Nitrogen (N), Phosphorus (P) and Potassium (K) are macronutrients.

As we discussed earlier, these macronutrients are important in different ways. Here are some of them.

These nutrients provide energy to the plant to make food. Plus, they develop the root and shoot of the plant.

These nutrients are involved in the making of chlorophyll, amino acids, proteins and other substances as well. If you apply it correctly, it can enhance the beauty and greenery of your lawn.

Over here, I want to talk about Sulfur as well.


Sulfur is a macro element in plant nutrition. Here’s why it is important.

A Plant makes amino acids, oils, and protein by using sulfur. Moreover, it is used to form chlorophyll. And it can also activate many vitamins and enzymes.

Sulfur is absorbed by the plant in the form of sulfate.

If I talk about its application, only 10 to 30 pounds of sulfur per acre is used by plants. You can increase the soil acidity by adding elemental sulfur.

Pretty simple, isn’t it?

  • It leads to optimum photosynthesis as it encourages vibrant foliage.

Let me explain.

Foliage refers to the leafy part of your plant or tree. Over here, note that the main function of a leaf is to produce food by photosynthesis.

Further reading:

When To Fertilize Your Lawn in Florida? | The Ultimate Guide

7 Great Uses of DAP Fertilizer

Urea Fertilizer | 5 Amazing Uses

As I mentioned above, it also provides support for fruit and flower production. Due to increased nutrient availability, the plants’ tolerance toward pests may increase as well.

  • Since it is a balanced fertilizer, it can be a good fit for indoor and outdoor plants.

Indoor and outdoor plants usually need multiple macronutrients. So when the triple 18 fertilizer is added to poor soil, it can provide even nutrient availability.

This promotes healthy growth. Amazing, isn’t it?

Summary: If we talk about the uses of 18-18-18 fertilizer, it is water-soluble. As a result, the nutrient levels are not affected by leaching and erosion. Plus, it is a balanced fertilizer and encourages vibrant foliage.

How and When To Use Triple 18 Fertilizer?

You can apply the 18-18-18 fertilizer by spreading slow-release granules or as a liquid when watering. In some cases, fertilizer spikes can be effective as well.

how to use 18-18-18 fertilizer

Spikes release nutrients in the soil gradually.

Before planting a new sapling in poor soil, add some granules of the triple 18 fertilizer. This will lead to a fast establishment of your plant.

After plantation, you can also apply a water-soluble option. Over here, let me introduce water-soluble powder to you.

You can dilute powder fertilizers with water. At the time of plantation, they can lead to good growth. But they can “burn” your leaves as well.

For vegetables, you can have better options as well. But if you apply 18-18-18 fertilizer after transplantation, you can get a good outcome as well.

Can I use 18-18-18 Fertilizer For Citrus or Lemon Trees?

Quick answer: Yes you can. But there are better options as well.

Lemon trees require a slow-release balanced fertilizer. Plus, all citrus trees require plenty of energy.

This is the reason why Nitrogen-rich fertilizers can work best for them. Let me explain.

The triple 18 fertilizer is a stronger mix. Therefore, an 8-8-8 fertilizer can work best for a lemon tree. Talking about its application, here’s what you need to know:

  • You should apply the fertilizer throughout the growing season. If you are using a liquid fertilizer, then apply weekly.
  • For the amount of fertilizer, follow the package instructions carefully.

This is because the amount will depend on the size and age of your tree.

  • Nitrogen applications should continue throughout the year.
  • It should not be applied in winters when the tree is not growing.

Now, let me tell you how to use the fertilizer properly.

Before adding fertilizer to your lemon tree, read the instructions on the package carefully.

If it says “water-soluble“, then dissolve your fertilizer in water first. Then apply the fertilizer to the leaves when the soil is soaked right above the root zone.

If you are using a granular fertilizer, spread the fertilizer evenly by hand. You can also use a fertilizer spreader.

To prevent your trunk from “burning”, apply the fertilizer at least two inches away from the tree trunk.

Then, water the soil and allow it to penetrate to the roots.

Note: Apply the fertilizer in a circle, equal to the height of the tree. By this, the fertilizer will reach the root system of the tree.

For example: Let’s say that your tree is 10 meters long. The perimeter (circumference) of the circle should then be 10 metres roughly.

For citrus and lemon trees, remember that they require more Nitrogen as they get bigger.

Can I use 18-18-18 Fertilizers For Potatoes?

Quick answer: It can be used at the time of planting. But we have better options as well.

Here’s a thing.

Growing potatoes can be a bit tricky. They need well-draining soil, full sun and a temperature between 50-70 ℉.

Can I use 18-18-18 fertilizers for potatoes

But which fertilizer works best?

Before talking about this topic, you should know that potatoes have a high nutrient requirement. Here are some side nutrients important for potato growth:

  • Boron: It improves potato skin texture. Plus, it allows calcium to be absorbed from the soil.
  • Magnesium: It causes better growth in low pH (acidic), and sandy soils.
  • Manganese: It decreases the pH of high-pH soils.

You should change fertilizers when growing a potato plant. Let me explain.

The potato plant requires around 3 to 4 months to develop. So here are the requirements at each stage:

  1. At the time of planting: A triple 15 fertilizer (15-15-15) is ideal. You can use 18-18-18 fertilizer as well.
  1. 1-2 months after plantation: A fertilizer high in Nitrogen (such as 34-0-0) is required.
  1. For last month before harvest: At this stage, the plant requires more Pottasium. So 14-7-21 fertilizer can work best at this stage.

If I talk about the amount of fertilizer, 25 pounds is added to a 1,000-square-foot potato garden (generally). In short, you can apply the triple 18 fertilizer at the time of plantation.

Can I Use Triple 18 Fertilizer For Grapes?

If fertilizers are applied correctly, the growth of grapes can improve massively.

In short, it depends on your soil. But for grapes, you can go for other options as well. Let me explain.

Nitrogen is extremely important throughout the process.

It is essential for fruit development. If you use a proper fertilizer, the size of the grape will be bigger. Plus, the growth will be faster as well.

Talking about phosphorus, its main function is to ensure strong, deep and healthy roots. This will help the grape plant to absorb more nutrients during its early stages. Potassium:

Potassium serves the purpose of protection for the plant. The potassium in the NPK fertilizer will lead to the healthy growth of the grapes. Plus, it will protect them from various diseases.

The NPK 18-18-18 fertilizer can be a good source of Nitrogen (N), Phosphorus (P) and Potassium (K). But, an ideal fertilizer is 10-10-10 for grapes.

Wrapping Up:

With this, our topic “what is 18-18-18 fertilizer used for” has come to an end.

In short, this NPK fertilizer is a great source of macronutrients for plants. This fertilizer can be good for the maintenance of your lawn and garden as well.

Remember that over-fertilizing your plant can cause chemical burns. So you should be extremely careful when using this fertilizer.

To recap, we discussed the uses of triple 18 fertilizer. Plus, we learned whether it can be used for potatoes, grapes and lemon trees or not.

If you have any questions, feel free to get in touch. Stay tuned for more.

What is 18-18-18 Fertilizer Used For? | Best Guide

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