Nutrients (nitrogen) are introduced onto crop fields.

(Credit: https://pixabay.com/en/users/sbj04769-5725676/. Creative Commons License)
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.
Details
Image Dimensions: 640 x 495
Date Taken:
Location Taken: US