In a new FarmVille sponsored link provided by American Express, they are offering farmers Double Crop and Tree Mastery for one week after placing the exclusive Amex Centurion Statue on your farm!
This sponsored link can be found under the bottom right of your FarmVille game screen. Click the link that takes you to Amex's Facebook Page. Then click the button to get your code. Copy your code. Next, click the Redeem Code button which will take you to a Zynga's redemption page. Enter your code in the box provided. Upon successful completion you will receive a notice that tells you that you've receive a free Amex Centurion Statue. Go to your FarmVille farm and check your Gift Box. The Amex Centurion Statue can will be in your Gift Box.
To turn on Double Mastery, you must place the statue on your farm.
You will have until December 12th to get your redemption code for the FarmVille Amex Centurion Statue.