This clever loop relies on a critical mass of basic lands to continually fuel itself while recycling its own pieces through the graveyard. By casting Early Harvest, you untap your lands to generate the massive amount of green mana needed to power Shigeki, Jukai Visionary's channel ability. Discarding Shigeki lets you fetch both Early Harvest and Regrowth right back to your hand, and casting Regrowth then pulls Shigeki out of the graveyard so you can start the cycle anew.