Until 6 PM EST on February 21st you can redeem the codes that will be given out throughout the week. Each code will feature a special item that is sure to help you get more of that farming done! The first round of codes were posted today and are:
harvesterfun – this will let you use the harvester for three hours
happyspinning – this is a code for a free spin on the wheel
Simply enter these codes on the "barcode" on the News page to redeem them for your useful farm items. Remember to keep checking back here as we will continue posting the codes as they are released!
Source: Game homepage