PPT Slide
Just an observation, but we rarely, never is probably more accurate, have any significant yellowing of our seedlings in the heat of summer. We have not applied iron since we started using this tank mix in the eighties. I am not sure but I think the sulfur could be important in this matter. I added sulfur to our mix after observing better "greening" of seedlings that had Ammonium sulfate applied and reading that sulfur is important in nitrogen utilization by plants. I wonder if the sulfur doesn't have some additional effect besides nitrogen utilization.
As you and I have discussed, I also believe our weed control is better with our tank mix.
At Augusta Forestry Center we use Uran and liquid Ammonium Sulfate (mostly on the pines) on both pines and hardwoods with good success.