From Brotato Wiki
Harvesting increases by an additional +8% at the end of a wave (stacking)
Crown is an in-game item that can be bought from Shop or can be found in a Crate. Most Items increase the Stats of the player while some of them provide unique effects.
Crown is a unique item. Unique items can only be bought or found once per run.
The Crown increases the amount of Harvesting you gain at the end of the wave by 8%. The Crown can provide large amounts of harvesting if found early. See the Harvesting page for more details.
Note that the Crown stops functioning after wave 20 when playing Endless Mode as the Harvesting Skill begins to decline.
The Crown is particularly powerful on characters with high amounts of Harvesting, such as Farmer or Entrepreneur.