Bowl Of White Plant Fertilizer
nitrogen fertilizer 1
(Image credit: ADragan)

Your garden isn't growing as well as it used to and some of the plants in the garden are starting to look a little yellow. You suspect a nitrogen deficiency in the soil, but you are unsure how to correct it. "Why do plants need nitrogen anyway?", you may be wondering. Nitrogen as a plant fertilizer is essential to proper plant growth. Let's look at why plants need nitrogen and how to correct a nitrogen deficiency in the soil.

Why Do Plants Need Nitrogen?

To put it in simple terms, plants need nitrogen to make themselves. Without nitrogen, a plant cannot make proteins, amino acids, and even its very DNA. This is why when there is a nitrogen deficiency in the soil, plants are stunted. They simply cannot make their own cells. If there is nitrogen all around us, as it makes up 78 percent of the air we breathe, you may also wonder why do plants need nitrogen if it is everywhere? How is nitrogen made accessible to plants? In order for plants to use the nitrogen in the air, it must be converted in some way to nitrogen in the soil. This can happen through nitrogen fixation, or nitrogen can be "recycled" by composting plants and manure.

How to Test Nitrogen of Soil

There is no homemade way to test the nitrogen of soil. You will either have to have your soil tested or purchase a soil testing kit. Typically, your local extension office will gladly test your soil for a small fee or even for free, depending on where you live. When you have your soil tested at the extension office, they will also be able to tell you any other deficiencies you may have. You can also purchase a kit as a way how to test nitrogen of soil. These can be found at most hardware stores and plant nurseries. Most are easy and quick to use and can give you a good idea of the nitrogen content of your soil.

Fixing a Nitrogen Deficiency in the Soil

There are two routes to go when fixing a nitrogen deficiency in the soil, either organic or non-organic.


To correct a nitrogen deficiency using organic methods requires time, but will result in a more even distribution of the added nitrogen over time. Some organic methods of adding nitrogen to the soil include:


Nitrogen as a plant fertilizer is common when purchasing chemical fertilizers. When looking to specifically add nitrogen to your garden, choose a fertilizer that has a high first number in the NPK ratio. The NPK ratio will look something like 10-10-10 and the first number tells you the amount of nitrogen. Using a nitrogen fertilizer to fix a nitrogen deficiency in the soil will give a big, fast boost of nitrogen to the soil, but will fade quickly.

Heather Rhoades
Founder of Gardening Know How

Heather Rhoades founded Gardening Know How in 2007 and built it up to what it is today.