Yield contests are part of Cooperative Extension's rich history. Today, yield test contests require an extension agent or USDA employee to be present and verify the yield of a three acre section of a field. County winners are then in the running for the state yield contest. They also have categories for irrigated and dryland corn with individual winners for each category. State winners are then in the running for the national yield contests. Today, some seed companies also have their own version of these contests that are run similarly, but require the grower to use one of the company's varieties in order to participate.
To learn more about yield contests, contact your local Extension office.