Homeowners Guide to Choosing the Right Fertilizer for Lawn

By: Ken Wilson

Are you looking for a one-stop guide on how to know what fertilizer to use on your lawn? The confusing three numbers and endless options on the market can quickly leave homeowners in a pickle. Luckily, these instructions will leave you 100% clued up on all the technicalities.

To choose the best fertilizer for your lawn, you should first understand the NPK ratio, test your soil, consider the season, and find which type will work best for your needs. You need to consider synthetic vs. organic, liquid vs. granular, and controlled vs. quick release.

Choosing the correct type of fertilizer for your lawn ensures optimal nutrient supply and prevents the chances of your grass burning. This quick read will give you all the all you need to know in four easy steps.

How to Know What Fertilizer to Use on your Lawn

In your search for the best lawn nourishment, it’s common to feel baffled on what option you should pick. These steps provide you with all the knowledge necessary to make a confident decision – and will have your grass looking lush in no time!

Step 1: Understand the NPK Ratio

The number one question that needs to be cleared up is the NPK ratio. You’ll notice that fertilizers have numbers on them, such as 16-4-8. These numbers are ultra-important to give your soil the right amount of nutrients. N stands for nitrogen, P stands for phosphorus, and K is for potassium. It is always in this order.

The numbers show what percentage of each nutrient the fertilizer is made up of. So 16-4-8 means 16% nitrogen, 4% phosphorous, and 8% potassium. The formula to calculate how many pounds of each nutrient there is in a bag is: the nutrient in percentage (e.g., 0.16) x the weight of the bag.

The three nutrients do the following:

  • Nitrogen: Promotes growth and makes grass greener
  • Phosphorous: Helps roots grow
  • Potassium: Prevents diseases and promotes general health

You can apply your grass needs to the NPK ratio, so if you want greener grass, you need more nitrogen. Conducting a soil test is a key way to determine what percentage to buy.

Step 2: Test Your Soil

If you want to ensure you have the best option for your lawn, a soil test will tell you the exact NPK levels that need attention.

Gather 7 to 10 samples from unfertilized soil 6 inches deep, like in this video. Your tools should be clean and rust-free. Samples should come from various places on your lawn and be mixed before testing.

You can buy an at-home test from a nursery, garden center, or online. You can learn how to read the results here. If you want an accurate test, you can send your sand samples to a soil-testing laboratory, which you can find with an online search. The best is to use a soil-testing company.

Understanding your soil type: Your soil type determines how fertilizer reacts to your lawn. Sandy soil means your fertilizer will drain quickly and will need a long-acting fertilizer and application more frequently. Clay soils need better root growth; therefore phosphorus is more necessary.

Step 3: Consider the Season

The season plays a vital role in when you should fertilize your lawn. You get warm-season and cool-season types of grass. Warm-season lawns benefit from early spring, early summer, and early fall fertilization. Cool-season types should get fertilized in early spring, early fall, or late fall (never summer).

Generally, spring fertilizer needs to be low in nitrogen of less than 10%, summer needs a lot of nitrogen of 20%, and fall requires a higher percentage of phosphorus and potassium. Note that there may be laws about phosphorus usage on your lawn. If you choose a season-specific fertilizer, use it only in the corresponding season.

When to fertilize:

  • Newly laid grass or seeds need fertilization with high phosphorus when planted.
  • The best time to fertilize is a few days after mowing.
  • You should apply fertilizer in the morning or early evening to avoid burning your grass.

Step 4: Decide on your Own Type of Fertilizer

Last but not least, on the decision-making agenda is understanding the qualities you will come across. The best option for you depends on your needs; luckily, you have many choices combining characteristics. Be sure to read the labels thoroughly to make certain that you know what you’re buying.

Synthetic vs. organic: Synthetic fertilizers are cheaper and offer faster results but run the risk of polluting the environment and killing the organisms that help keep soil nutrient-dense. It is made from chemical compounds.

Organic options like manure and compost may need multiple applications but offer a slow release of nutrients that are good for the soil long-term and microorganisms within. If animal waste isn’t your thing, there are still organic aerators and liquid dethatch options.

It is usually better to choose organic if you can. If you want the fast-acting and effective results of synthetic options, make sure they are environment-safe and aren’t harmful to your pets.

Granular vs. liquid: Granular fertilizers are easy to distribute and need watering to activate their properties. This option also offers a slower release, which lasts longer than liquid but doesn’t have immediate results. Liquid options are easy to apply and fast-acting but may need multiple applications and leave patches if not evenly distributed.

Controlled vs. quick-released: Slow-release or controlled formulas are better for the long term. Most organic options are controlled release and promote lawn growth for up to several months. Quick-release options might give you faster results and seem more appealing, but may also cause your grass to grow faster and more frequently – which means more maintenance.

Pre and post emergent fertilizers: You get formulas that are called weed-and-feed fertilizers. This means that they contain herbicides that control the growth of weeds. You get pre-emergent options that prevent weed growth from happening. Post-emergent formulas kill weeds that have already grown.

Final Thoughts

Now that you know about the NPK ratio, you can test your soil to provide it with the necessary nutrients. Always consider the season before fertilizing your lawn and choose an option with the qualities you need.

Organic and slow-release fertilizers are usually your best bet. If you are looking for the quicker, more effective results of synthetic fertilizers, ensure the formula is safe for the environment and your pets.

About the author 

Ken Wilson

Long time career in the home services industry from remodeling to patio construction. Currently residing to in SWFL and active contributor to multiple home & garden publications.