hay, hey

Hay or hay means dried grass used as fodder or bedding for farm animals--
Farmers once cut their own hay to feed the horses or oxen that pulled their wagons and plows.
Mowing the hay was once the occasion for a party that might last for days.

Hey or hey ( rhymes with hay ) is an expression of greeting, surprise, or emphasis--
Hey, how have you been?
"Hey there, you with the stars in your eyes..."

Now that you know that, you can say--
"Hey, don't leave that hay out to rot in the rain!"