If the nettles are not poisonous to hogs (I have no idea about this, but many animals are not affected by seemingly poisonous plants), then I would put 28 hogs on the acre for a day and let them have at it. They will leave the soil looking like the surface of the moon and perfect for replanting. Be sure they have water. If hogs won't work, maybe 150 goats. Or 4,000 chickens (or 1,000 chickens rotated for four days on quarter acre paddocks). In any case, it needs to be waaaaay more animals than the land will support for even a normal day. That will give you the animal impact as well as rid you of the plants. Hogs would be best if they are suitable. The animals will solve your fertility problem, too.
For long term prairie-like conditions, a rotation of 25 ducks or chickens on the acre would keep your land fertile, turned, and in tall grass. Search the Internet for "Chicken Tractor" and keep in mind that the concept works for ducks, geese, turkeys, hogs, goats, etc. Try to keep the livestock weight down to 100 pounds per acre, keep the animals bunched up into small herds (using fencing or tractors), and keep them watered. If you can set up a path that requires 25-50 weeks for one complete rotation, then you've got the plan working. The idea is for the grass to completely recover before letting the animals back on it. If you get the right ducks or chickens, you might end up with 2 dozen eggs per day all year, for a little extra income.