Nitrogen Fixation Lesson for Kids

Instructor: Shoshana Yarin

Shoshana has taught all grades with an emphasis in science and has a master's degree in science.

We know that plants need sun and water, but they also need a special food that comes from nitrogen. Organisms in the soil create fixed nitrogen, which is like fertilizer, so plants can grow healthy. Learn just how that happens in this lesson.

Do Plants Need Food?

Ever been so hungry your stomach was growling? You know that you need to eat in order to grow strong. Plants don't have a mouth or a stomach like you, but they do require food. People who take care of plants give them fertilizers, which are nutrients that help them grow. Wild plants can find these nutrients naturally in the soil.

One of these nutrients is nitrogen, a pure substance that makes up 78% of our air - that's right, there is far more nitrogen in the air than the oxygen we need to breathe. Nitrogen makes a molecule with itself that creates a very strongly bonded pair of atoms (that means they're connected or joined).

Nitrogen bonded
N2

This bond isn't easy to break apart, and plants can't use nitrogen in this tightly bonded form. The plants need help to break up the nitrogen and 'fix', or change, it into a different form. This process is called nitrogen fixation.

Nitrogen Fixation Process

Here is how nitrogen fixation works:

  1. In the soil are little plant helpers that change nitrogen by breaking it apart into a type of nitrogen called ammonia.
  2. Then, the ammonia combines with other substances, like hydrogen.
  3. Now the plants are able to use this new form of nitrogen as food.

When ammonia and hydrogen are combined, they make nutrients for plants. This is like natural fertilizer. Plants that get the right amount of air, fertilizer and water grow nice and big and that's good food for us!

Plants need fixed nitrogen from the soil to grow from seedlings to strong plants
seedlings and sunflowers

Understanding Nitrogen Fixation

Have you ever taken a soda can from a six pack? You wouldn't very easily be able to drink a soda if it was still bonded together with the other five sodas. You have to separate the soda first. Then imagine changing the original form of the soda by pouring it into a nice glass of ice. The original six pack is like the bonded nitrogen, and the can you break off is like the ammonia. The hydrogen is like the ice cubes in the glass. When the soda and ice are combined, they make a drink for us, just like when the ammonia and hydrogen are combined, they make nutrients for plants.

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