NPK: Lawns

You’re researching fertilizer products and come across a lock combination of numbers - the NPK ratio. This metric of the three main nutrients found in fertilizer hold serious significance when it comes to growing grass and caring for your lawn. 

Even so, these numbers aren’t understood well and misuse of fertilizer can cause damage to your lawn and harm to the environment, not to mention wasted time and money for you. At Sunday, we’re here to help! We’ll break down NPK, what it means for your grass, and why NPK ratios matter.

What Does NPK Stand For?

NPK stands for nitrogen (N), phosphorus (P), and potassium (K). These three nutrients comprise 70% of the mineral nutrients that you find in grass plants and are the same nutrients grasses need to function properly.


Why Does Grass Need Nutrients?

Just like us, plants need essential nutrients (17 to be exact!) to survive and for sustained, healthy growth. Air and water provide carbon, oxygen, and hydrogen, while your soil provides the majority of the remaining nutrients your grass needs to be healthy. 

In most cases, lawns really don’t need an excessive amount of fertilizer applied because most of what plants need is found right where they are – your soil. Not all soils are perfect though, so Sunday has developed a fertilizer program that gives grass proper levels of nutrients using a better way to ‘NPK’.

What Does NPK Tell You About a Fertilizer?

Let’s get back to basics – what really IS fertilizer? Fertilizers are regulated products by government agencies that require a minimum guaranteed analysis of the 3 major nutrients your lawn needs: nitrogen, phosphorus, and potassium (NPK). N, P, and K are the primary nutrients required to sustain a thriving lawn through the growing season while all other nutrients (remaining 14) are required in much lower amounts. 

For most fertilizers, NPK is available in the form of nitrogen as is (N), phosphorus as phosphate (P2O5), and potassium as water-soluble potash (K2O). The ratio of these three nutrients listed on a fertilizer product designates the percentages by weight of what nitrogen, phosphate, and potash are within that product and the ratio will always be written exactly in that order (N-P-K).

What NPK Doesn’t Tell You

While NPK can tell you exactly how much of each major nutrient you are applying to your lawn – the NPK ratio doesn’t tell you where these ingredients come from, what form of nutrients you’re receiving or what nutrients your lawn needs (or doesn’t!). So, just because you know your fertilizer NPK values, doesn’t mean you know what you’re applying and why. Here’s where Sunday and your soil test can help.

Risks of Over-Fertilizing

For decades, nutrients like nitrogen and phosphorus have been applied excessively on lawns. If you can believe it, annual US fertilizer consumption for turfgrass is estimated to be 2.7 million tons, valuing nearly $5 billion dollars annually. This practice of overuse is causing most lawns to be over-fertilized, causing significant impacts to lawn function and the environment.

Sunday Approach to NPK

With Sunday, you can join us in our goal to reduce excessive fertilizer (and chemical!) use. The main difference between Sunday and ‘the other guys’ lies beneath the lawn – your soil. Our nutrient program is based on a comprehensive soil test dialed in NPK and interpreted using Minimal Levels of Sustainable Nutrition (MLSN) method, providing you with only the nutrients science tells us your lawn needs. 

Essentially, Sunday is supplementing the basic needs of your lawn, versus taking control of your lawn. Avoiding dependency on fertilizer and ultimately, helping your lawn be more resilient over time.

Sunday Sustainability Tip: Did you know phosphorus is banned in about 10-12 different states? We did that homework for you. That’s why Sunday does not include phosphorus in custom plans unless your soil test shows a major deficiency or you’re starting your lawn from scratch

Ways to Introduce NP and K Naturally

We do our best to supply nutrients in the most responsible way by using forms of the nutrients most effectively utilized by plants (e.g. your grass!) Bonus? Sometimes we’ll supply the NPK in more natural forms like our soy protein that serves as an organic nitrogen boost.

Here are some other ways to naturally introduce NPK to your lawn ecosystem: 

nitrogen: key driver of growth and deep green color for grass

  1. Clover lawns! Introducing Sunday Grass Seed like Lucky Lawn or allowing clovers to grow in your lawn can help with organic nitrogen-fixing of the soil. 
  2. Grasscycling helps return nitrogen found in grass tissue to your soil. Simply remove the bag off your lawnmower before cutting the grass and let the clippings do the work for you.  
  3. Increasing organic matter in the soil will also lead to organic and increased availability of nitrogen. 
  4. Introducing more humic acid which leads to increased uptake of nitrogen, water-holding capacity, and more aerated soil. 


phosphorus: supports root growth, seedling development, cell division, and the absorption of nutrients 

  1. Mowing and mulching leaves can lightly and responsibly introduce organic forms of phosphorus to your lawn too. 

Sunday Sustainability Tip: Avoid phosphorus pollution by using compost and organic materials sparingly on your lawn. While composting is generally positive, if applied to lawns excessively it can lead to nutrient leaching into waterways.   


potassium: helps convert food to energy and increases turgor, keeping your grass standing up right! 

Use Sunday products with seaweed. Seaweed is rich in many essential nutrients for grass including nitrogen and potassium.

Cited Sources

Landschoot, P. Turfgrass Fertilization: A Basic Guide for Professional Turfgrass Managers. Penn State Extension. 

University of Minnesota. Quick guide to fertilizing plants. UMN Extension. 

Heffer, P., et al. Fertilizer Outlook 2010 – 2014. International Fertilizer Industry Association. 

Hongzhang, K., et al. Global pattern of leaf litter nitrogen and phosphorus in woody plants. INRA, EDP Sciences.