They only grow wheat?

In my minecraft village, they only grow wheat, although I initially sowed carrots, potatoes and wheat in the fields, now there are only wheat fields. How can I change this?

As far as I know, you can't change that, even with me they only grew wheat at first, but then differently. I think they decide for themselves what they want to grow and what not. They're farmers… Laugh. Maybe you can convince them to act differently to grow something.