Open carry allowed? Cite please
The law doesn't tell you what you can do, it tells you what you can't do. Open carry is not prohibited in Iowa, nor is carrying in a park. Prohibited places include schools(and school buses), casinos, the state fairgrounds, and buildings on the capitol complex. You may also not carry while operating a snowmobile or ATV. If you are in a "weapons free zone"(within 1000 feet of a school or in a park with the exception of park land designated for hunting) you are subject to twice the penalty if you commit an offense involving a firearm.
You should read this. It's a good summary.