Q: What did the farmer say when his hay started blowing away?
A: Hay, come back!

Explanation:  Hay is grass that has been cut, dried, and stored for use as animal food, especially for cattle, horses, goats, and sheep.

“Hey” is a word used to get someone’s attention such as when someone says, “Hey, you guys!” or “Hey there!”

This joke is funny because it uses “hay” instead of “hey” when calling the hay to come back.  “Hey” is also used in the Beatle’s song “Hey Jude.