NPK: Garden

If you’ve ever looked at a bag of fertilizer, you’ve probably noticed the three numbers printed in bold across the label. These dashed digits indicate the amount of the three main nutrients (nitrogen, phosphorus, and potassium) found in the fertilizer. N, P and K are essential for promoting plant growth, flowering, and fruiting. An imbalance of these nutrients could result in a less productive garden. Understanding these numbers, what they stand for, and what role N, P and K play in the garden can help you grow better this gardening season.

What Does N-P-K Stand for?

Plants require 17 essential nutrients to survive and thrive. Three of those – carbon, oxygen, and hydrogen – are gathered from the air or water. The other 14 are gathered from the soil. But soil doesn’t always have the right amounts, and different plants need different levels of different nutrients, at different times. 

That’s where fertilizers (and those 3-digit numbers) come in. Fertilizer is basically plant food. The dashed numbers on fertilizer bags indicate the ratio of nitrogen (N), phosphorus (P) and potassium (K) in the mix: N-P-K. More specifically, the ratio of these three nutrients actually refers to the percentage by weight of nitrogen reported as free nitrogen, phosphorus reported as phosphate, and potassium reported as water-soluble potash. 

Sunday ProTip: Now that you know what the fertilizer NPK values mean, check the ingredients list to see if your nutrients are synthetically or naturally derived.

Why are N, P, and K Important?

These three nutrients are macronutrients, or nutrients needed in the greatest amount by most plants. But what do they actually do for your garden plants? 

  1. Nitrogen is essential for overall plant growth. 
  2. Phosphorus helps with root growth and flower, seed, and fruit development.
  3. Potassium helps the plant fight off disease, manage water use, and enhance overall plant hardiness. 

Sunday ProTip: Compost your garden waste and veggie scraps to return nutrients for your garden!

Sunday and Garden Fertilizers

We want to supply nutrients in the most responsible way by using sustainable, natural forms of the nutrients most effectively utilized by plants, whenever possible. Our All Purpose, Flower & Bloom and Veggie & Tomato garden fertilizers use natural ingredients like composted turkey litter and feather meal to provide good-for-your-plants and good-for-the-planet nutrients to boost your garden’s growth. Bonus? Our garden fertilizer ingredients help build soil organic matter, which helps foster healthy, happy soil over time.

Cited Sources

University of Minnesota Extension. Potassium for crop production

University of Minnesota Extension. Quick guide to fertilizing plants