Nutrients (nitrogen) are introduced onto crop fields.
![Airplane spraying crops in a field.](https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/styles/full_width/public/thumbnails/image/wss-qw-nitrogen-spraying.jpg?itok=d82mNNQW)
Detailed Description
Fertilizers and other chemicals are applied to crop fields worldwide. Due to runoff, excess chemicals can find their way into water bodies and harm water quality.
Sources/Usage
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