Fertilizer Numbers 101

Home » Blog » Fertilizer Numbers 101

What Are Fertilizer Numbers and Why Do We Need Them?

The best looking lawns, gardens, and plants all have one thing in common – they need specific nutrients to flourish. While dirt offers most of these nutrients, not all soil is created equally. For plants to thrive, test the soil to understand the pH levels better, and identify which nutrients are lacking. Many homeowners rely on fertilizer to assure plants receive the necessary nourishment, but fertilizer numbers leave many scratching their heads, trying to figure out what they mean.

Which nutrients do all plants need to survive?

There are three specific nutrients that every plant needs to grow. Nitrogen (N), phosphorus (P), and potassium (K) are often referred to as macronutrients. Different plants require different combinations of these nutrients.


Nitrogen is well-known for its ability to turn a dull lawn green in the spring and summertime. This happens because the chlorophyll that creates the green hue is made up primarily of nitrogen. When the ground has an insufficient amount of nitrogen, grass, plants, and leaves don’t turn a bright emerald color. If you start to notice the leaves or grass blades take on a yellow hue, low nitrogen levels are likely the cause.


Phosphorus creates healthy roots in plants and is necessary during times of seeding and blooming. If leaves and stems start to take on a purplish or yellow hue, doesn’t bloom, and looks unhealthy, it can be a sign that the soil pH levels are off-balance and in need of additional phosphorus.


Potassium is necessary for the formation of chlorophyll in a plant and helps minimize disease in your backyard. It is challenging to identify a lack of potassium without a soil test. However, if plants don’t produce blooms, look unhealthy, or have small fruit, it can be a sign of a potassium deficiency.

Understanding Fertilizer Numbers

Each type of fertilizer offers valuable information on the label to help you make better decisions for lawn care. To understand the combination of macronutrients in the fertilizer, look for a series of three numbers near the product name in this format: 1-1-1. This is known as the N-P-K ratio or the amount of nitrogen, phosphorus, and potassium in the fertilizer. Each number identifies the percentage of that nutrient found in the bag. For instance, if the ratio is 25-5-5, then the fertilizer contains 25% nitrogen, 5% phosphorus, and 5% potassium. Use soil test results to find the perfect match for your backyard.

If you plan to add fertilizer to your backyard this year, understanding the different combinations and how they are labeled on fertilizer bags is a vital step in lawn care.  For additional assistance with proper lawn care, contact Perennial Lawn Care today!

Posted on
Perennial Services