Farmers have shrugged off a sluggish U.S. ec­­onomy to post three consecutive years of record farm income, but a reversal could come hard and fast, economists warned at last week’s Iowa Farm Bureau Economic Summit.

"I have a very positive outlook for our future, but I’m concerned about the bumps in the road," said Michael Boehlje, Purdue University agriculture economist. "I don’t want you to be road kill."

Agriculture booms like the one farmers...