On a warm July morning, three busloads of young people ranging in age from 14 to 25 roll through flashing yellow traffic lights before dawn in Kearney. It’s necessary to get ahead of the blistering summer sun. For the next four to eight hours, these workers will carry out a summer job long considered a rite of passage for young Nebraskans: Corn detasseling. For decades, this intense work has been a summer staple for thousands of kids growing up …