The first question to ask is... what animal are you going to market this hay for? If you are selling to people with cattle then what they want around here is alfalfa and preferably in big bales. For horses, most want a straight grass hay in small squares. Alfalfa can be too rich for sheep and goats too. A little alfalfa can be good so maybe you just want to overseed.
I have horses so I am trying to get my hayfield into producing some good straight grass hay. It had been seeded to a standard crp mix, probably 25 years ago and then left neglected. All that is left is a lot of bad brome, poison parsnip and queen Ann's lace. We have been keeping it mowed and are now getting ahead of the weeds. I have started with some manure teas that I mix with fish emulsion, molasses, epsom salts, and bone meal. I haven't been able to afford a sprayer yet so have just been hauling the tea out in tubs in the back of the pick up and tossing it willy-nilly. Not perfect but better then nothing. I am wanting to save up some money for lime.
I understand the idea of disking. It was explained to me that you don't want to set it deep and you don't want to turn over anything. But it opens the ground like aeration and makes a place for seed to go, if you are overseeding an existing hayfield. It will also allow more moisture to get into the soil *if* you accomplish it in spring. It is something you want to do before you seed or feed.
Then there is the question of the grass types. It isn't just the grass itself and the nutrients but whether or not it has endophyte issues, etc. Most grasses are pushed because they are what the industrial cattle market can use. I will be going old school and seeding some orchard grass to start and slowly work at complimenting that. Hopefully as I fix the soil the native grasses will return. They are now even questioning health issues of clover for horses. But my good news is that I already have someone I can direct market to if I can get my grass up to par.
My BIG picture is to put a hedge row/ forest garden completely around my hayfield so that i have the best of both worlds. Composted waste from the horses and garden will all end up on the hayfield and that is more then enough garden to keep me busy as the hayfield is right around 22 acres. My pasture will be handled differently. Because of the hoof wear and tear, bunch grasses will be discouraged and I want to try to seed pasture to a combination of buffalo grass and bluegrass. Both are sods but don't get the height on them that most hay grass requires. I also need to start importing earth worms. I don't know exactly what all my land has endured, but even after three enlistments in the crp program the worms have not returned. I need to jump start that process.
Of course there is that caveat that I could be totally wrong, but after three years of cleaning up weeds, cutting thistle, mowing, picking up handfuls of soil and spending a lot of time starring at grass, this is the plan that I have come up with.