Around here, if i happened to see a buck like that on more than one occasion in the same field, i would certainly try and bow hunt him because there is no way that i would catch a mature buck in a field later on in the fall (during rifle season). The bucks are pretty much feeding at night in the alfalfa fields during rifle season. The only way to catch them in rifle season in a field is when they are trailing a hot doe. So I guess it depends on your area. If there is a chance the buck won't be there later on, you won't gain anything by waiting. The setup will be tricky however... using bales as a basis for a blind might be the best way to go. good luck!