Careful with the seasoning on those hay bales, you have to use lots of nitrogen(chick poop) to get them ready for planting, but need to balance that out before putting the sweet potatoes in. Unless you just want the leaves for the chickens.
When I pull out the straw bales from the coop in the spring, I always save the 3 best intact bales for planting my sweet potatoes in. They grow fabulous that way and saves land space for other crops.
I have never relied solely on store bought feed for my chickens, though they have that available 24/7. I grow a lot of food but struggle in the wintertime to supplement them as much as I like. They are fed a plate of oatmeal/wet fines with mixed greens and blueberries topped with a thyme...