So, it appears that Y'shaarj's buried beneath the vale of eternal blossoms (according to the new scenario, Dark Heart of Pandaria).
we know that the trees and flowers in the vale are always blossoming. we know that the water from the vale is the reason why the pandaren grow humongous vegetables in the valley of four winds. but what is it that makes that water so special?
IMHO, it's y'shaarj. his body is rotting beneath the valley, and that's highly nutritious to the land! dead old god is the best fertilizer ever!