Hi William...
What was being grown on the land? Are we talking about one big uniform field of monoculture? How much land is there and how much do you think you will be able to farm using the methods you are comfortable with?
First thing, I would get to know the guy who was farming the land if that relationship hasn't been too damaged. He will know what he sprayed on there. Some of the other neighbours might know what was sprayed, or would at least remember what he grew the last few years and could help you guess what was sprayed. It's worth getting to know these guys even if you don't see eye to eye with how they farm...you might need their help someday..
It makes a big difference, learn about what sprays were used and find out what the 'residuals' are...some things are pretty persistent for several years, others break down quite quickly and i wouldn't lose too much sleep or years of effort over...it will be easier to make sound decisions if you know what you are dealing with...group 4 chemicals are bad news if you're going to try veggies...if it's just glycosates i wouldn't worry about it next year, your exposure would be way less than what you've probably been eating all the time if you go out to a restaurant or buy food at a store at all...
Next up, if it's been farmed commercially with herbicide weed suppression there is going to be a Huge weed seedbank, and probably some rhizomatous perrenial weeds that have been suppressed but are still spread all around. I know, I know, weeds are our friends and the solution, etc etc...but don't underestimate how this can smack you, it could quite possibly overwhelm whatever you try planting...especially if you're talking about a lot of acres... If you can walk it now you might be able to get some idea of what's lurking there for next spring.
Do you have the equipment to handle the entire acreage or are you thinking of just using a bit of it?
If you leave something like that fallow you're not going to get any kind of nice
native plant community in ten years, it's going to be an insane tangle of the worst weeds and invasive plants in your area, with a huge seed bank built up and lots of perrenials and it will be a nightmare to deal with organically later on... If it was more land than i could farm, i would think about hiring someone or I would try myself to get the fallow land into the most aggressive smother-crops possible, maybe a nice soil building polyculture...not sure where you are, but i'm thinking something like rye and alfalfa and clover and field peas and forage oats and try to overwhelm the weed pressure...your land's already been cultivated like crazy so i would get in there and work it again one more time or two in the spring to take out a bunch of the annual weed germinants and give the stuff i'm sowing a half a chance...there will be lots of years for min til or zero till later on..
..maybe you can graze it too...if it seems pretty clean you could eventually try to establish perrenial pasture on a bunch of the land, as something that can be profitable but is low maintenance without big machinery and chemicals...i'd pick a small manageable chunk to try growing some crops on, and i'd pick a bunch of different crops just to see what works for you and what you like doing and what the market is, and i'd expect to be overwhelmed with weeds in that area especially on the first year...
i'm just finishing year two of essentially the same
project, my advice from experience is don't be too much of a purist, you will get it converted over to the way you want it eventually but you might need to make some compromises in the first year or two to get past the land's history...and don't bite off more than you can chew...i'm still renting out something like a hundred acres, it would
be nice to fix it all at once but it would be a disaster, i can deal with maybe ten acre chunks every couple of years, and i'd rather someone else kept up with the status quo on the rest so it will be easier for me to handle later on..
good luck!