A nitrate is a chemical compound made of nitrogen and oxygen atoms bonded together. You encounter nitrates more often than you might think: farmers spread them on fields as fertilizer to help crops grow strong and green, and food companies add them to bacon and ham to preserve the meat and give it that distinctive pink color.

The nitrogen in nitrates is like food for plants. When farmers add nitrate fertilizer to soil, plant roots absorb it and use the nitrogen to build proteins and grow tall. Without enough nitrogen, plants turn yellow and weak. That's why nitrates have helped feed billions of people by making farms more productive.

But nitrates can cause problems too. When too much fertilizer washes into rivers and lakes, it feeds algae that grow out of control, blocking sunlight and using up oxygen that fish need. Scientists monitor nitrate levels in drinking water because high amounts can be harmful, especially for babies.

Chemists write nitrate as NO₃⁻, showing one nitrogen atom connected to three oxygen atoms. Different nitrates exist, including potassium nitrate (used in fertilizer and fireworks), sodium nitrate (found in preserved meats), and ammonium nitrate (a powerful fertilizer).