I would recommend conditioning the soil to help boost the amount of bacteria that suffered from AAtrex and Atrazene. Round-up used on a cornfield? No matter what Monsanto promised, the new formulations are no different from the old ones.
Medina Soil Conditioner sold by the gallon or 2.5 at Home Depots. Follow label and till, repeat. One gal should do 10 acres.
Innoculation of the bare root with a paste made-up including several different michorrizal fungi before planting, and a touch of bone meal for phophorous. Corn is a vehement depleter of Nitrogen so this is one case I would suggest supplementing. Perhaps 10 lbs per acre with anhydrous ammonia before tilling.
I would also drill a symbiant ground cover that fixates nitrogen like alfalfa - instead of clearing all other "competing" ground cover.
6.5 is a good pH but Iowa isn't known for calcium overloads, acidify if need be.
I'd also recommend the plantation alter row cropping of trees with differing pine species - important if viral or bacterial problems are present in the nursery stock. If you're dead-set on the reds, get half from one source and half from somewhere else, or try white pine peripheries or Scotch pine every few trees.
Garlic and wild onion and pennyroyal on the boundaries for critters.