Polk County farmer Brad Moeckly welcomed about two dozen elementary students into his hog barn last fall and didn’t worry a bit about disease or liability issues.

The same goes for Steve Lee, who took a classroom full of school kids along for a ride in his combine without worrying about any of them being injured on his farm machinery.

And there were no complaints from students about chilly April weather, muddy shoes or long bus rides two weeks ago when Candi Engler showed two groups of 4th through 6th graders from Cowles Montessori School in Des Moines the conservation improvements she and her husband Ben have made on their northern Polk County farm.

That’s because the three...