I'm sure farm jokes have been around since mankind discovered agriculture or, conversely, since Abel and Cain had the following exchange:
Abel: That peculiar odor, it seems to be coming from the plowed field. What can it be?
Abel: For the land's sake.
That's actually one of the jokes Louis Untermeyer includes in his "Down on the Farm" joke section. They don't get much better. Here are a few more:
It was in Kentucky; the night was dark. Two men banged on the old cabin door. "Joe and me, we just found a body down in the holler, and we were afraid it might be you. It was too dark to tell."
"What did the body look like?"
"About your height; sort of scraggy--"
"Did he have on a shirt?"
"Was he shaved?"
"I think so."
"Well then, it warn't me."
That's actually a good one.
Now, I don't mind farm jokes. I live in a farming community (though I'm not a farmer; Dad was a bricklayer, I'm a technical writer). We did watch the occasional Hee-Haw episode. I've made it my 2011 resolution to learn how to eef:
I've even got a good one for ya, learned from a guy who spent some time in Tennessee. It's not really a joke, per se, just a play on how some folks in the country talk, he says. Here it is:
SAR2. CDEDBD eyes?
That's it. Just say the capitalized letters (and number) as you would reciting the alphabet. Hopefully you get the humor. If not, don't blame me -- I'm just passing the joke on.
Here's one more from Mr. Untermeyer:
It was Farmer Brown's first visit to the big town. In the window of the department store he read a sign: "Ladies Ready to Wear Clothes."
"Gosh," he said. "It's about time."