What Does NPK Mean on a Fertilizer Label? NPK Ratio Explained.

A bag of fertilizer is emblazoned with several key pieces of information, one of the most important being the NPK data.

But what exactly is NPK and is it important to consider these numbers when shopping for the best fertilizer for your lawn? The short answer is yes! The “NPK” on a fertilizer label stands for nitrogen, phosphorus, and potassium, the three primary nutrients plants need to grow.

Fertilizer bags feature 3 numbers on them.

  • The first number shows the ratio of nitrogen in the fertilizer
  • The second number represents the ratio of phosphorus.
  • The third number is the ratio of potassium

The formulation is, therefore, an N-P-K fertilizer, whether it is a liquid concentrate or even a granular feed.

Some fertilizers may contain other elements such as humic acid, fluvic acid, iron, etc. These give additional benefits. Speaking of which, do you know why iron is important for grass growth? More on these below.

N is for Nitrogen

nitrogen benefits

It is a macro-nutrient that is key for feeding lawns. Almost all grass types rely heavily on nitrogen for their development. Nitrogen is important for the following purposes:

  • Shoot development
  • Root development
  • Color of the lawn
  • Recuperative ability of the lawn
  • Growth rate and density

P is for Phosphorus

Phosphorus benefits

Phosphorus is also an important major nutrient in the best fertilizers for Bermuda grass lawns.

It is important for the general well-being of the lawn, especially when growing a new turf. In a starter fertilizer, phosphorus will help with faster root development as well as a good growth rate.

Most yards already have adequate phosphorus. However, you may still need to put down a good starter fertilizer for Bermudagrass to help it develop deeper roots and out-compete weeds.

To determine how much phosphorus to put down in your lawn, take a soil sample and send it to the soil testing laboratory. You’ll be advised on how much of this nutrient to apply, which will also help you choose a good fertilizer for your lawn.

K is for Potassium

Potassium benefits

Potassium has some great benefits and it is very important to look at this number when shopping for the best fertilizer for your home turf.

It would help if you put down some potassium to help your lawn become more drought-tolerant, especially in the summer days.

While some varieties of grass do better than others in the summer, you’ll want to get a fertilizer that has some amounts of this nutrient in it.

Potassium in lawn fertilizers has the following benefits:

  • Helps with cell growth and development
  • Drought resistance
  • Improves rooting

Now that you know the role of those 3 letters on your fertilizer, you’re right to think that the top-rated products we reviewed would be best for your needs. The first place to start should always be soil testing to gauge your pH level.

If your soil returns a high phosphorus level then you will want a fertilizer with a low to 0 rating for the P. ie. 12-0-5

I have reviewed lots of fertilizers with various NPK ratios for all types of grasses and have broken them down here:

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