I don't think the clover is your problem. It doesn't fix that much nitrogen. I don't think you need Round-up. Till it good in the fall and twice in the spring, if you can. Add some wood ash and a couple bales of clean shavings and try again. If you want to try killing the clover, I don't think Round-up would exacerbate the problem though.
My go-to book officially says there is no antidote for too much nitrogen. The only cure is water and time. Water will eventually leach it away. You could try building it up a bit with some soil from the field. That may help dilute your soil a bit.
Wish I could be more help. Heck, if I were closer I would help haul dirt in.
Good luck!
Last edited by Bowker Acres on Wed Sep 12, 2012 10:53 pm; edited 1 time in total (Reason for editing : My english teacher didn't make me do enough homework and I still have poor spelling.)