NPK Soil Science

NPK – The Science, What They Are and What They Do

Lawn Fertilizer Numbers

Quick Pro-Tip’s:

  • Nitrogen (N): nitrogen is the food that aids a lawn to grow quickly, taller, and develop a darker green color.
  • Phosphorus (P): phosphorus is responsible for root growth and helps aid new lawn development
  • Potassium (K): potassium is a nutrient responsible guards the plant against diseases and aids in drought protection and cold tolerance.


You look outside and notice your grass is brown, patchy, and generally dry looking.  So, you decide to head to the store to get some fertilizer. But, what do all those fertilizer numbers mean?? And, what do you need for your lawn??  Well, the short answer is that it heavily depends on a professional soil test (free with the Lawn Serv program). But, more on that later. For now, let’s take a quick look at those fertilizer numbers, what they are, and what they mean for your lawn.

how to test soil

What The “Fertilizer Numbers” Are:

  • Nitrogen (N), the first number: nitrogen is the food that helps a lawn to grow quickly, taller, and to develop a darker green color.
  • Phosphorus (P), the second number: phosphorus is responsible for root growth and helps aid new lawn development; phosphorus is often “0”, or very low, as there are restrictions around when and where phosphorus can be applied.
  • Potassium (K), the third number: potassium is a nutrient responsible for guarding the plant against diseases and aids in drought protection and cold tolerance.

These are three of the core nutrients used to amend soil to grow a lush green lawn. It’s what you see on the front of a fertilizer bag when you see for example 20-10-10 (or 20N-10P-10K).  That is the percentage (by weight) of the three major nutrients required for healthy grass growth, always in the same order nitrogen-phosphorus-potassium (N-P-K). Why don’t the the percentages equal 100 percent? That is because there are other nutrients and filler product in fertilizer mixtures. This filler helps to apply the nutrients evenly over an area.

N-P-K Organic Fertilizers (plant-based):

If you are looking for an organic option, your best bet is to find a plant-based, manure-based, or blended version of the NPK fertilizer. This allows for a balanced fertilizer that stimulates through beneficial soil microorganisms and improves the structure of the soil providing long term benefits. Some plant-based NPK fertilizer are developed with alfalfa meal, soy meal, seaweed based, and cottonseed meal. These organic plant based fertilizers break down easier and have faster absorption than most.

So, What Do These “Fertilizer Numbers” Mean For Your Lawn?

These numbers are very important as your grass needs different percentages depending on what time of year, climate, and soil composition.  For example, your lawn may need a boost of Phosphorus if you’re applying new seed, or may need a boost of Potassium late in the season to promote deep root growth for the winter.  The best way to determine exactly what your lawn needs is through a professional soil test, which we offer free as part of our Lawn Serv subscription box! And, as always, feel free to reach out with any questions; we’re here to help!

Cheers!

The Lawn Serv Team

Best Lawn Process