Super Harvest is the way of showing that you are receiving additional XP from harvesting a crop. It was added on July 12, 2010. Previously, it would show File:XP-icon.png experience, which really wasn't visible. As such, it was changed to make it more noticeable. In order to receive a Super Harvest, a farmer must harvest crops which have been fertilized; either by a neighbor, or with a Fertilize All.