Wild onions shouldn't be a problem, unless you've got wild pigs in the area...in which case, you won't need to worry about tilling! They'll do it all for ya!
With soil like that, have you considered alfalfa? It does well with a pH over 6.8 and can be an excellent perennial that stands up to a fair amount of grazing. A single field that is half white clover and half alfalfa would be a pretty solid bet for keeping deer around most of the year.