we do some custom farming, so we have the luxury of seeing some different practices, and their results.  this year, and years past, we did some pre plant nh3, fall nh3, preplant 32%, and sidedress.    year in year out fall nh3 gives us the best yields.  


  the preplant applied 32% probably comes in second, issues with that are, has to be worked in pretty quick, or rain at least a 1/2'' to carry it into the soil, can the product be applied in a timely manner, and is the application equipment up to the task of applying 30-50 gal acre evenly---have seen some real train wrecks with this.  also compaction is a issue.
 
 spring nh3 can work okay for us. but it has to be applied deep enough not to cause seed burn, have to wait for the ground to become somewhat fit, and compaction can be a problem also.

 as far as fall applied urea or ammonium sulfate or breaking down stalks, in our area it doesn't work, too far north.