Nitrogen Cycle Diagram
Free printable nitrogen cycle diagram — a labeled illustration showing nitrogen fixation, nitrification, assimilation, ammonification and denitrification. Download PDF or PNG for Letter paper.
How nitrogen moves through the cycle
The nitrogen cycle is how nitrogen moves between the air, the soil and living things. Here is what happens at each labeled part of the diagram:
| Process | What it does |
|---|---|
| Nitrogen in the atmosphere | About 78% of the air is nitrogen gas, which most living things can't use directly. |
| Nitrogen fixation | Bacteria turn nitrogen gas from the air into forms plants can use. |
| Nitrification | Bacteria change ammonia in the soil into nitrates. |
| Assimilation | Plants absorb nitrogen through their roots to grow. |
| Ammonification | Decomposers break down dead matter, releasing nitrogen back into the soil. |
| Denitrification | Bacteria return nitrogen gas to the air, completing the cycle. |
Companion worksheet
A free fill-in worksheet with an answer key, built from the labels above — students match each process to its description, then answer a couple of short questions. Great for a quick check after using the diagram.
How to print
Choose Download PDF for a ready-to-print file that fits US Letter paper (8.5 × 11") in landscape, or Download PNG for the high-resolution image.
Frequently asked questions
What is the nitrogen cycle?
The nitrogen cycle is the way nitrogen moves in a loop between the air, the soil and living things, through processes carried out mostly by bacteria.
Why do living things need nitrogen?
Nitrogen is used to build proteins and DNA, which every living thing needs to grow.
What paper size should I print this on?
The diagram is sized for standard US Letter paper (8.5 × 11") in landscape orientation. Use "Download PDF" for a print-ready file that fits the page automatically.