surfactant helps the chemical"stick" so to speak to the weed - without actually being sticky. It helps the water droplet that is carrying your chemical to essentially stick to the weed vs rolling off of it is the best way I can explain it. It sort of removes the wax froom your car hood - for another visual. A waxed hood the water will bead up and run off. Remove the wax and the water spreads out and "sticks" more. Which is what you want on your weeds. The ammonium sulfate (21-0-0) is actually a nitrogen fertilizer which helps get a good kill on grasses. The fertilizer promotes growth and absorbtion of nutriants and thus the active chemical in your herbicide. Ammonium sulfate also helps condition the water if you have high levels of iron (like in well water in my area) and thus restricts the free iron in the water from binding with the active chemical in your spray and thus weakening it. That's about the best way I can explain what these are and how they work at least as I understand it.