Choosing Lawn Fertilizer: NPK Ratios and Soil Testing Guide for Healthy Grass

Truly, it doesn't matter if you are paying a lawn fertilizer service, or performing the fertilizing yourself.

Either way, adding supplements to your lawn is the same principle as humans using a multi vitamin. 

The idea is to give your lawn the nutrients that it is missing.

This guide will walk you through the key steps to achieving a lush, green yard, starting with understanding NPK ratios and soil testing. 

Keep reading to learn how to fertilize like a pro and transform your lawn.

Why is Proper Fertilizing so Important for a Green Lawn?

Here’s the deal, proper supplementation is crucial to turning an average lawn into the pride of your street. 

It's important to note that the key word in that sentence is "proper". 

Just like with properly dosed multi-vitamins, you want to add the right amount of the missing nutrients that your lawn is in need of. 

Step 1 to Proper Lawn Fertilization- Preparation 

The first and arguably the most important step for you to take is to research your lawn. 

You want to know what nutrients your soil is missing. Therefore you want to find out what you need to add, instead of gambling with generalized lawn supplements. 

To do this start by testing your soil with an at home soil test kit. You'll be able to find at your local garden center or online. 

Best of all, these tests are super simple and give you a better idea of what your soil is missing. 

Almost all of these kits include NPK tests, which measure the levels of Nitrogen, Phosphorous and Potassium in your soil. These are the THREE main elements in lawn fertilizers. 

Pro-Tip! Most people don’t know this, but you can also SEE what nutrients in the lawn are missing. For example, light green or yellow plants or grass suggests a lack of nitrogen. Pretty cool right!?

Step 2 to Proper Lawn Fertilization- Choose the Right Fertilizer

So now you know your lawns nutrient levels, you now have to pick out a lawn fertilizer. 

But that’s not all, you also need to know how much to add to get to the optimum levels.

Once you understand these levels you'll be able to more effectively choose the right fertilizer for your lawn. 

Understanding the Numbers

When you look at the fertilizer package you'll often see that it's a 20-10-10 fertilizer or something similar. 

This represents the percentage of the product that is Nitrogen, Phosphorus and Potassium respectively. 

You might be thinking, why don't the numbers don't add up to 100 percent, right? 

Well, that’s because the rest of the weight is taken up by filler ingredients which are needed to ensure a correct spread of the fertilizer. 

Optimum Measurements of NPK in PPM

Here are the numbers when it comes to the optimal PPM for the lawn's nutrients.

For Nitrogen: the optimum ppm level (parts per million the concentration of the element), is in the 20's. This works out to around 70-100 pounds per acre. 

For Phosphorus: ppm should be between 40 and 100. 

Finally, Potassium: levels can fluctuate quite a lot but anything above 250 is good.

What about pH?

When it comes to pH you’ll want to try and achieve a level of 6 or 7, which is roughly neutral and optimum for grass growth. 

Step 3 to Proper Lawn Fertilization- Fertilizing the Lawn 

More and more fertilizers on the market are boasting that they are "slow release" which is exactly what it sounds like. The fertilizer granules will slowly breakdown, releasing the nutrients over an extended period of time. 

The point of this is to reduce the frequency you have to fertilize your lawn and hence reduce the time you have to spend on it. 

Why Not Use Liquid Lawn Fertilizer?

There are certainly types of liquid lawn fertilizer that are beneficial. 

However, it's generally much better for you to use granular fertilizer as opposed to a liquid spray. This is mainly because granular lawn fertilizer helps to ensure that you get an even coverage. 

Sprays can be too easily affected by the wind, which will prevent you from getting that perfect coverage that we desire. 

How Many Times A Year Should You Fertilize the Lawn?

Gardenaholic recommends 5 fertilizer applications over the season, starting in mid-April or once your grass starts to grow, whichever is first. 

You should plan your 5 applications over the entire season, up until frost will set in. Ensuring that each fertilizing session is equally spaced apart. 

Be Careful Not to Overspread the Lawn Fertilizer!

When you're actually spreading your fertilizer you must be careful not to overdo it. It might be easier to start with your spreader on a "tighter" setting, i.e. letting out less. Then you can put half the recommended amount in and see how far it gets you, before finishing the rest appropriately.

It's best to do more applications on a tighter spreader setting to avoid over fertilizing the lawn.

How often should I test my lawn's soil?

Test your soil at least once a year, preferably in the spring, to accurately adjust your fertilization strategy based on its current nutrient needs.

What is the best time of day to apply fertilizer?

Fertilize your lawn in the early morning or late afternoon to minimize evaporation and increase nutrient absorption.

Can I fertilize my lawn if it's going to rain?

It's best to fertilize before light rain, which can help dissolve the fertilizer and carry nutrients to the roots. However, heavy rain might wash away the fertilizer, so avoid fertilizing if a storm is expected.

How do I know if I'm over-fertilizing my lawn?

Signs of over-fertilization include yellowing or burned grass, excessive weed growth, and thatch buildup. If you notice these signs, reduce the amount of fertilizer and increase watering to dilute the concentration of nutrients.

Bottom Line on Proper Lawn Fertilization

Professional landscaping companies all over the United States will agree that supplementing your soil is crucial to growing a gorgeous and healthy lawn. 

However, to enable yourself to supplement the lawn appropriately you will need to plan and prepare. 

The best method to properly fertilize the lawn will always be to test, apply and retest. 

With the correct supplementation a greener lawn is within reach.