There is a nice article that was written in a recent edition of Corn and Soybean Digest featuring Grower Ed Winkle.
The article looks at nitrogen management and it focuses on getting an understanding of the nutrients that are in the soil and using that information to determine what type of application is needed.
Ed is very good at keeping people informed and his willingness to share information is very much appreciated by growers and supporters like myself. Check out his blog! http://hymark.blogspot.com/
Picture Source Jdickert