This is called zipper ear in corn - entire rows or parts of rows missing, usually found on the underside of the ear or the outside part away from the stalk. The precise cause is unknown, but the zippering is thought to be associated with lack of pollination of ovules in that area or aborted kernels. Poor pollination - silks on that side of the ear may be late-emerging, buried or hidden under a mass of other silks where pollen did not reach them. Aborted kernels- excessive heat or drought shortly after pollination can cause kernel abortion near the tip or on one side of the ear.