blockgame.register_abm({
	nodenames = {"bg_terrain:grass"},
	interval = 15,
	chance = 4,
	action = function (pos, node)
		if blockgame.air_flows_through(pos + blockgame.vector.dirs.up) then return false end
		minetest.set_node(pos, {name = "bg_terrain:dirt"})
		return true
	end,
})