Many of the "wheat fields" shown in the movie - other than stock footage - are actually alfalfa fields. The location shots were filmed in the area around Arvin, California, where there isn't much wheat but there are huge areas of farmland consisting of alfalfa, which is used to feed the thousands of cows in the surrounding dairy farms.
One of over 700 Paramount Productions, filmed between 1929 and 1949, which were sold to MCA/Universal in 1958 for television distribution, and have been owned and controlled by Universal ever since.