system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why do farmers plant sunflowers around corn fields?
gpt
Corn crops leave an excess of Nitrogen in the soil.

Sunflowers can be planted as a follow-up to take advantage of that.  They like the nitrogen-rich soil.

Farmers used to do this with soybeans as a pairing but found that the soybeans had various problems that the sunflowers do not have.

But the short short answer to this is "because they found it to be most profitable to do."  That at least speaks to the motivation.