Understanding Plant Nutrition

Based an article written By Minda Daughtry and updated by Rhonda Gaster, North Carolina State Extension

Many gardeners apply 10-10-10 fertilizer every year because that’s the way they’ve always done it, and it’s easy.

We know that a balanced diet is important to our own health. Just like us, plants can flourish or flounder depending on the nutrients they have. Not all plants need the same exact “diet” so the menu you provide should match what the plant actually needs. How do you know what the plant needs?  A soil test, done every three years or so will give you everything you need to “Know Before You Grow”.

Plants require 17 essential elements for growth. They obtain hydrogen (H), oxygen (O), and carbon (C) from water or as a gas via the atmosphere. The remaining 14 nutrients must come from the soil to help plants flourish. The quantity of macro and micros needed varies by type of plant, but they are all required by the plant for growth. 

Macro-elements: nitrogen (N), phosphorus ℗, potassium (K), calcium (Ca), magnesium (Mg)  and sulfur (S).

Micro-elements: boron (B), chlorine (Cl,) copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni) and  zinc (Z)

Providing a complete and balanced “fertility menu” that contains all the essential elements is important. More is not better! Too much of a good thing can throw the system out of balance and may cause harm from deficiencies or toxic build-ups. For example, if too much phosphorus is provided, it can obstruct the uptake of other elements and lead to iron, manganese and zinc deficiencies. Or if there is too much potassium it creates either a calcium or a magnesium deficiency.

Also, you should know what kind of nitrogen you’re putting out for the plant. Read the label on your fertilizer package to identify what form of nitrogen it contains. There are basically two categories:

  1. nitrate-nitrogen: This form promotes compact plant growth and is used when we want to avoid stretched out plants due to excessive overgrowth.
  2. ammoniacal nitrogen and urea: Many organic fertilizers have nitrogen in these forms. Using ammoniacal nitrogen and urea-based fertilizers after plants have been transplanted helps them get a good start and encourages a flush of new growth.