A mastery bonus is an amount of XP earned by a farmer when harvesting a premium crop. A crop becomes "premium" when it is: a) planted from a seed that has already been mastered by the farmer; and, b) randomly selected by the crop's bonus chance. Such a crop will appear bigger than a normal crop — exactly like a mature, fertilized crop. Although mastery signs seem to indicate that they are somehow connected to premium crops, they are merely decorations. Only mastery itself — and a bit of good luck — are required to receive a mastery bonus.