Infinite colored manaInfinite untap of basic lands you control
How it works
Activate the basic land with Fertile Ground attached by tapping it, adding at least 1.
Fertile Ground triggers, adding .
Activate Earthcraft by tapping Soliton, untapping the basic land.
Activate Soliton by paying , untapping it.
Repeat.
If the basic land is an Island, you may add mana of any color using Fertile Ground's trigger, and you may infinitely repeat steps 3-4 with any other basic land you control.