If the US needs more agricultural workers, why not go the same way as Australia by offering a 1-2 year working holiday visa for 18-45?
People could also learn a skill such as getting a driving licence for a combine harvester and also people doing degrees in farm management and agricultural studies could gain valuable experience doing a stint out in the midwest and helping to harvest the Weetabix.
The Dole Pineapple manufacturing plant and plantation on Hawaii also requires much needed seasonal workers.
Make the visa system more open and flexible to get them in worldwide for up to two years at a time. Some promising employees may also be able to stay.