Plant Nutrients – The “BIG THREE”: Nitrogen, Potassium, and Phosphorus

Nitrogen, Potassium and Phosphorus are crucial for plant health. As the seasons, and nutrient demands, of various crops change, I figured to start a three-part series highlighting the elements that are needed by most crops. To prevent these blog posts from becoming too large, I will be breaking them up to discuss the big three, the mighty macro’s, and the much-needed micros. I am not putting them in order of importance since all plants need all of these nutrients in one formula or another. To start we will discuss the main three nutrients you might already be familiar with, Nitrogen, Potassium, and Phosphorus.


Nitrogen (N) – This element is essential to plant growth and development. Inside the plant, nitrogen is used as a building block for various key parts of the plant, including chlorophyll, amino acids, and proteins. Nitrogen is classified as a mobile plant nutrient, which means that the plant has the ability to transport this nutrient from different locations based on where it is needed. These aspects are key to diagnosing nitrogen deficiency in plants. If a plant is suffering from lack of nitrogen, the top, youngest growth may have a green appearance while the older leaves may have a light green/yellow appearance. When nitrogen is in excess, the foliage should be dark green and should have excessive growth.


Phosphorus (P) – Think of this nutrient as the powerhouse of the plant. It is used for energy inside of the cells of the plant and as a major building block of DNA and RNA. Research shows that phosphorus is needed for root development, increased resistance to plant diseases, and flower development. This nutrient is also considered mobile, like Nitrogen. The key with mobile nutrients is to look at the older tissue on the plant and compare it to the younger tissue. The signs of phosphorus deficiency can also be tricky to diagnose. Deficient plants will often suffer from a lack of growth in the early stages. More severe symptoms may appear later, and the leaves may have a purple hue to them.  


Potassium (K) –   This is the “health” nutrient of plants. Potassium is used in plants to control water regulation and different functions in plant metabolism, and to control how the plant responds to stress events. Like the two nutrients discussed earlier, potassium is also mobile in the plant. One of the most important functions of potassium is the buildup of the nutrient in the root system of the plant. This buildup of potassium in the roots helps the plants bring water up to the plant. The signs and symptoms to look for with deficiency include yellowing on the edge of the leaves, sometimes deformed leaves, and stunted growth of leaves or roots.


This is a very brief overview of the three main nutrients that plants need. There is a lot of good information available for the grower to use to help educate themselves on the topic of plant nutrients both online and in other resources. In hydroponics, it is crucial to understand the basics to help improve your crop health. Of course, if you have questions feel free to reach out to any of us at CropKing and we can help you answer any of your questions. Look for parts two and three on the blog in the coming weeks!


Bonus Fact: Has anybody wondered why potassium has the elemental symbol of K instead of P? The word potassium comes from the old English work “Potash” meaning pot ashes and the Abric word “Qali” meaning alkali. The symbol K comes from the Latin work “Kalium” meaning alkali. Now you know the history and the reason we use K to stand for the elemental form of potassium!


NPK nutrients hydroponics hydroponic