The Nitrogen Cycle Lesson for Kids

Instructor: Emily Lockhart

Emily has taught science and has a master's degree in education.

The nitrogen cycle is essential for the survival of living organisms on our planet. Most nitrogen is contained in the Earth's atmosphere, and living organisms need a way to access that nitrogen. We will follow the cycle to understand how this happens.

What is the Nitrogen Cycle

Farts are pretty funny. They are stinky and make us giggle when they are loud and disrupt class. But scientists take this 'gas' pretty seriously--our farts contain a very important particle called nitrogen (written as N2). About 60% of that smelly flatulence is nitrogen, and nitrogen is essential to our survival--it can be found in everything from your hair to your organs. In fact, the air you breathe from the atmosphere is about 78 percent nitrogen (most of Earth's nitrogen is in the air).

Unfortunately, plants and animals don't absorb nitrogen from the atmosphere. So, while there's plenty in the air, plants and animals need different ways to access the nitrogen. The processes that help get nitrogen out of the air and into living organisms is called the nitrogen cycle. This cycle moves nitrogen from the air to the soil, from the soil to living organisms, and from living organisms back into the air and soil.

Let's explore these three processes of the nitrogen cycle below.

From Air to Soil

Nitrogen (N2) is taken out of the air three different ways:

Nitrogen Fixation

The first is called nitrogen fixation. This process is done by bacteria found in the soil. Bacteria are living organisms and are so small a microscope is needed to see them. Specialized bacteria can pull nitrogen from the air and pass it along to the soil in a form that plants can use. Some plants, like peas and beans, make great hosts to these bacteria. Inside the plants, the bacteria take the nitrogen from the air and convert it into usable forms for the peas, beans or other nearby plants. If the bacteria cycles the nitrogen from the air into usable forms in the soil, then plants can access it through their roots.


When it strikes the ground, lightning provides another way for cycling nitrogen from the air into the soil. The nitrogen in the air reacts with the lightning and forms a product called nitrate (NO3). This product is a liquid and washes into the soil.

Manufacturing Nitrogen

Humans have found a way to manufacture nitrogen gas into a usable product. This product is sold commercially to farmers who put the usable nitrogen on their crops. Environmentally, this can cause damage when overused, because excess nitrogen can seep into the streams and lakes. This can cause certain algae to thrive and build up on the surface of the water, poisoning or crowding out other essential plants.

The nitrogen cycle
Nitrogen Cycle

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