I don't know what nh3 flow divider system you were using on your toolbar however the knives adjacent to the plugged one are not necessarily going to put down extra are they? 

In fact most typical rental toolbars can be +/-25% or more from row to row even if total flow rate on the monitor is correct. If one knife is plugged and your total rate stayed the same the excess would likely be spread over all other rows, not just the adjacent ones, in most nh3 systems.  I don't think your plugged knife and streaks is necessarily relevant to the 60" side dressing discussion. 

It does bring up the importance of having not only the total flow rate controlled but having that total flow uniformly divided among the different row units.  Here is where the ANH3 high pressure type system shines. I believe it is much more accurate row to row than most common systems in use.

Jim at Dawn