Pope,
You still have plenty of time to plant. I respectfully disagree with fishinty. A soil sample is always best, but with what youre looking at planting at this point in the year, definitely not necessary. Wheat, oats and rye are often planted by professional farmers to condition poor soil. They plant it when the soil has been depleted of nutrients and then till it in as green fertilizer. You could do that and till yours in next year if you wanted. The point is, they will grow on less than ideal soil. I see youre in Iowa. Rape and turnips would be a good option, and by planting them now until early August you wont have to worry about bulb rot. Soilman's seed selection is exactly what I would go with. He has some great advice. Mine is basically the same. I am far from a professional land manager, but here is what I would do for what it's worth:
Day 1. brush hog (it sounds like you've already done this)
Day 2. What a week and spray with generic roundup (glyphosate)
Day 3. Throw a bag or two of 19-19-19 fertilizer down. (A few hundred pounds of lime on a half acre will never hurt).
Fertilizer and lime may not be necessary. But, they will definitely help the nutrient value and attractiveness of the plot. It's all up to what you want to spend. Work the field up with whatever you have available. Choose your seed and broadcast it. Then drag it or drive over it to work the seed in
Day 60. Kill something eating in your field
We plant in northern Wisconsin as late as the first week in August. You have plenty of time a little further south. Good luck! Let us know how it goes.