I will tell you after reading your post what pops in my mind first. On soil health it is very important and without it you don't have a foundation to grow anything. Hay pulls a lot from ground and is hard on it so if you can find a good source to buy and it is reasonable that is what I would do. Buy it when you don't need it. Hay equipment, inputs the whole deal is expensive. Try to feed hay, if this is what you do, in a way where you can spread nutrients out on your ground. If you are converting row crop ground to grass you will probably have to spend some money on inputs because most row croppers mine ground out. They don't want anything left much after they take the crop.