In the Farmers Festival event, you earn contest points by harvesting crops. The more points you get, the higher you climb on the leaderboard and the better the prizes you get. To see your progress, tab on the event icon in the bottom right corner of the screen.
In addition to the usual prize for a place in the event, there is also a chance to get an exclusive reward. Join forces with a group of players that you were placed into during this event and score enough points to win it.