What percentage of the atmosphere is oxygen?

The atmosphere consists mainly of nitrogen, which makes up about 78% of the air we breathe, while oxygen accounts for approximately 21%. This percentage is critical for supporting life on Earth, as it is necessary for respiration in animals and plants. The remaining portion of the atmosphere comprises other gases, such as argon, carbon dioxide, and trace gases, which together make up the final 1%. Understanding the composition of the atmosphere is essential in the field of agriculture, as it directly impacts plant growth, photosynthesis, and overall ecosystem health. Thus, knowing that oxygen makes up 21% of the atmosphere is foundational knowledge in environmental science and agricultural studies.