Is there a difference in meaning between "put my foot on the ground" and "put my foot to the ground"?
"Putting your foot to the ground" is an idiom implying standing or walking on it, while "putting it on the ground" could just mean resting it there.
"He put his ear on the ground" conjures up a comical picture of someone detaching their ear and laying it down. If you put your ear to the ground you bend down and apply one ear to listen for footsteps etc.; a human being can't very well put both ears to the ground at once!