In order to have a healthy, lush, green lawn, you'll need to feed it. And, September is an ideal time to help your lawn recover from the long, hot summer. This segment explains what the numbers mean on the fertilizer bag, and looks at the differences between a quick or slow release fertilizer.

Produced by the Department of Communications at Kansas State University. For more information, visit our website at:

Fertilize for a Healthy Lawn

If you can only fertilize once, September is a very good time to do that. There are a couple of reasons why it’s an ideal time. Usually after the summer heat and drought, our lawn is ready for a good dose of food to recover from that. And, the weather gets cooler at that time of year – so the turf can utilize the food better at that time.

Vigorously growing lawns use a lot of nitrogen. Nitrogen isn’t always readily available in the soil, so it needs to be replenished on a regular basis. There are three numbers that you’ll find on a fertilizer bag. The first number represents the percentage of nitrogen, the second number is the percentage of phosphorous, and the third number is the percentage of potassium by weight within the bag.

Most of our soils in Kansas have adequate amounts of phosphorous and potassium. So, nitrogen is usually the one that is needed the most by your lawn. When we’re looking for a fertilizer for our lawns, it’s important to go for the largest “first” number, and smaller second and third numbers.

There are a couple of different types of fertilizer categories based on the availability of the nitrogen. They are commonly known as a quick release, which is a water-soluble form of nitrogen, or a slow release, which is a water insoluble type of nitrogen.

It’s important to look at the Guaranteed Analysis information. Usually, it’s on the back of the fertilizer bag, or near the bottom on the front of the bag. This one, for example, has an asterisk that points down and says that 1.5% of this bag is a slowly available nitrogen – this is out of the 16% nitrogen total. So, most of this fertilizer package is a quick release fertilizer. This one would be an ideal one to apply this time of year, in September, because it will quickly feed the turf before we enter into the fall period, and winter dormancy.

This feature story prepared with Chelsey Wasem, former Kansas State University Research and Extension Horticulture Agent, Johnson County. For more information, visit your local county extension office or visit our website at

Horticulture Newsletter

KSU Horticulture Newsletter

Get more information from our weekly newsletter.

Find Your Local Office

Have questions or need help?

Local Extension Office Map

Click the map to find your Local Extension Office.

YouTube Videos

YouTube Videos

Watch K-State Research and Extension Videos.

Kansas Healthy Yards Tagline