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Fertilizer Numbers: What They Mean and How to Use Them to Grow Better

Learn how to effectively use fertilizer numbers (NPK) for optimal plant growth by understanding their significance and applying the right proportions for different plant needs.

Table of Contents

If you want the healthy growth of your plants you use the fertilizer according to their requirements. However, the most important for you is to understand the number that is written on the front of the fertilizer bag. So, fertilizer numbers represent the N-P-K ratio which is the essential element for the plants that describe the amount of nitrogen, phosphorus, and potassium in a fertilizer.

Now, we will provide you the complete information about what the fertilizer numbers stand for and what they mean. Also, how can you use the fertilizer for the better growth of plants? So, continue reading, and don’t skip any points for better understanding.

What are plant fertilizers?

What are plant fertilizers

Simply fertilizer is plant food. Fertilizers have different types of nutrients that work like the food of the plants. It can be natural or deliberately put into the soil. Ever since people started plants for food thousands of years ago. They had to manage the quality of soil on the land. 

When soil contains lots of essential nutrients crop plants can grow fast and produce large yields. However, when we harvest crops and then take them away and eat them we take the nutrients too. So, after years of growing plants, the soil can not support crops very well unless we replace the nutrients using fertilizer. 

What is the classification of the nutrients? 

As we discussed above, nutrients are the most essential food for plants to grow but these nutrients are classified into different two categories: Macronutrients and Micronutrients. Plants require higher quantities of macronutrients and low amounts of micronutrients. So, you notice that in the fertilizer bag, the 3 three numbers represent. 

Hence, all 3 numbers do not contain all the 100% nutrients. Therefore, to understand 100% you must know the classification of nutrients. Also, we will later describe the example for better understanding. So, keep reading for proper guidelines.

Classification of nutrients:






Iron, Chlorine, 


Manganese, Boron

Calcium, magnesium, Sulfur 

Copper, Zink 

Also, they contain fertilizer that can be classified as either straight or mixed. Straight fertilizers contain only one nutrient such as urea which provides the plants only the nitrogen. However, the complete fertilizer contains all three major nutrients (NPK) nitrogen, phosphorus, and potassium.

What does NPK stand for?

In the fertilizer bag you watch the three numbers are listed. So, what is the number? So, these numbers (e.g. 10-2-0) on the bag that are associated with the fertilizer guarantee that it contains the fixed perception of the amount of NPK. These numbers are known as NPK ratio and it stands for: 

  • N For Nitrogen 
  • P for Phosphorus 
  • K for Potassium 

These essential ingredients are used in all fertilizers. It gets the term NPK for each element symbol on the periodic table and will always be arranged in an order.

What does the number of fertilizers mean?

So, you are looking at what that really means. However, each element of the NPK performs a unique task in healthy plant growth. The three nutrients nitrogen, phosphorus, and potassium are the essential food of the plants.

So, after testing your lawn or planted area soil, you can use the right bag of fertilizer after understanding their role in soil according to your soil requirements.  Hence, these numbers help you to choose the right fertilizer due to that the numbers show the percentage of the element that helps the plant to grow fast and healthy.

For example

When you purchase the bag the three numbers on the label are mentioned. For example: 10-10-10 which means it contains 15% nitrogen, 0% phosphorus, and 2% potassium. But note that this percentage is not 100% because it means that 83% contains the other nutrients that are not mentioned here but they are Calcium, magnesium, and Sulfur. 

What is NPK’s Role in agriculture?

NPKs Role in agriculture

These nutrients are a very essential part of the plants for their growth and root development. Here we discuss the role of N-P-K one by one. Let’s start. 

Role of (N) Nitrogen:

  • The role of nitrogen in plants is to produce growth faster and their leaves greenery.
  • Nitrogen is responsible for the greening of the plants and the shoot growth. 
  • A major source of Ni is soil: Organic matter( 95-99%).
  • N is an essential constituent of amino acids, proteins, nucleic acid (RNA & DNA), enzymes, hormones & secondary constituent of chlorophyll.
  • It is also essential in plant processes like photosynthesis. Nitrogen also affects the growth of plants and roots development. 
  • Impart dark green color to plant, encourage vegetable growth, and delay fruit ripening.
  • Content of N in healthy plant: 1-5%.

Role (P) Phosphorus:

The element phosphorus helps to grow the roots and also produce new plants.

Availability of P at different pH: 

  • Acidic: H2PO4-
  • Less alkali to neutral: HPO42-
  • More alkaline: PO43-
  • P is called the key to life(plants cannot complete their life cycle). P is a major constituent of nucleic acid, phytic phospholipid & ATP. It helps in the Storage & transfer of energy ( Energy currency)


  • Root development.
  • Nodule formation
  • Increase the ratio of grain/bhuna
  • Decrease lodging(provide strength to straw)
  • P(high)=Fe and Zn
  • Content of P in healthy plants: 0.1-0.4%

Role of (K) Potassium: 

  • Stomata regulation
  • Counteracts injurious effects of excess N in plants 
  • Provide disease resistance to plant
  • Formation & translocation of sugar 
  • Osmotic regulation (stress avoider) 
  • It is referred to as a quality nutrient but not effective without its co-nutrients like N & P
  • Content of K in healthy plants: 0.1-0.5%

How to use Fertilizer numbers to grow Plants better?

If you love planting then you must understand the several factors that affect the growth and development of plants. So, fertilizer is one of the most essential steps for planting. Hence, before selecting the fertilizer you know the requirements of your plants. Here I am going to discuss several factors one by one. 

  • Plant Type: 

First of all, you know the type of plant whether you are fertilizing ornamental plants, vegetables, fruit trees, or another specific plant. It is essential because all plants have different nutrient requirements.

  • Soil Test: 

One of the most important steps is the soil test which helps you to know the requirements of the plants in the correct form to select the fertilizer. So, This determines the current presence of the nutrient level in the area of the soil.

  • Understand plant needs: 

Now, in the next step, you know the plant needs which one you decide. So, when you purchase the bag of fertilizer you read the label that shows the three numbers(e.g. 12-12-12) These numbers show the percentage of the N-P-K in the fertilizer. 

So, match the nutrient needs of your plant with the appropriate fertilizer ratios. N promotes leafy growth, P supports root development and flowering, and K helps to resist plant disease and produce healthy production. 

  • Growth stage: 

use Fertilizer numbers to grow Plants better

When plants grow and pass through different stages then their nutrient needs change for example the stage of growth, flowering, fruiting, or more. So, use the fertilizer formulation that matches the needs of your plants. However, if you do not pay attention, it will not be beneficial for your plants, and the chances of damage of overdosage and incorrect use of fertilizer. 

  • Slow Release vs Quick Release: 

You also select the slow or quick-release fertilizer on your plant requirements. Hence, Slow-release fertilizers work slowly and provide nutrients to their plants over time. On the other hand, the quick-release fertilizer provides the nutrients immediately to your plants. 

  • Organic vs Inorganic: 

Also, learn the organic or inorganic fertilizers that contain different qualities. Organic fertilizers are derived from natural sources such as plants, animals, and manures but inorganic fertilizers are derived from the chemicals plus minerals from the earth. However, organic promotes long-term soil health and is better to use for plants growing and the after-effects. 

  • Use of fertilizer: 

The most important step is that you must read the manufacturer’s instructions that are mentioned on the fertilizer packaging. This is important to know the usage of your selective fertilizer due to incorrect usage or over-fertilization that can harm your plant’s production. 

  • Water the plants: 

Remember to give water to your plants after fertilizer which will help to dissolve the nutrients in the soil, and roots, and also resist burning roots. However, Note down avoid more watering just water the plants according to their specific needs.

  • Environmental Conditions: 

During the selection and application of the fertilizer, you must analyze the climate conditions of your area because the climate affects the plant’s needs and requirements for nutrients. Also, note that environmental factors like water quality, runoff, and local regulations affect plant growth and development. 

  • Adjust soil conditions: 

When you choose and apply the fertilizer you must adjust your soil conditions which means the pH, moisture, and presence of the other nutrients. As a result, some of the nutrients may be present in the soil but in very small amounts. Sometimes the use of the wrong method of fertilizer increases the amount of nutrients in the soil affecting the production of the plant’s disease and growth. 

  • Rotate fertilizer: 

Rotate fertilizer

This is the type of fertilizer that you can use to provide a balanced nutrient profile over time. The use of rotated fertilizer can prevent the depletion of specific nutrients in the soil. Also, that helps to reduce the buildup of pests and diseases that target specific crops. 

  • Fertilizer causes plants:

You notice that lost plants are just limping up and trying to survive. However, they struggle with nutrients and light. The reason is that the diseases and pets are continuously trying to kill or eat them. So, use the right fertilizer according to your plant’s requirements and also care for them at all stages of the growth because the nutrient requirements change with the growth and at different stages. 

  • Brand & formulation of Fertilizer: 

You also research the brand and formulation of the fertilizers because some brands only specialize in the limited plant type and offer the only unique nutrient in fertilization. So, you purchase the fertilizer according to your plant requirements after a soil test that helps you to protect your plants from any damage. 

How to choose the right fertilizer? 

As above we mention the different factors that you consider and then use fertilizer numbers. So, before selecting the fertilizer you must analyze all the considerations and apply them.  Now, below I am going to give you the steps to choose the right product for your plant requirements. 

N-P-K( Fertilizer number)

Fertilizer Type 



Balanced Fertilizer 

Use any stage of plant growth 


High in nitrogen 

Use for leaf growth and color 


High in phosphorus 

Use for flowers, roots development, and fruits 


High in potassium 

Use for roots and stems 

The number indicates the percentage of all ingredients in the fertilizer. So, if your plants require more nitrogen use a higher nitrogen number, if you need more phosphorus use a higher phosphorus number, and if you need more potassium use a higher potassium number.

Common Misconceptions

One common misconception is that more fertilizer always leads to better plant growth. Over-fertilizing can harm plants by causing nutrient imbalances and root burn. Another myth is that all fertilizers are the same. Different plants and soil types require specific nutrient ratios for optimal growth.

Many believe organic fertilizers are always safer than synthetic ones. While organic options are environmentally friendly, improper use can still damage plants and soil health. It’s also a misconception that fertilizers can replace good soil health. Fertilizers supplement, but cannot substitute, the benefits of well-maintained soil structure and biodiversity.

By understanding these myths, gardeners can make more informed decisions for healthier, more productive plants.

Wrapping Up:

Fertilizer numbers represent the NPK( N stands for nitrogen, P stands for phosphorus, and K stands for potassium) numbers which is the percentage of each specific element that is present in the fertilizer formula.

These fertilizer numbers help you to choose the correct fertilizer for your plant’s requirements. So, before purchasing the fertilizer you must test the soil that you use to plant which helps you to know the requirements of your plants.

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