It is not necessary to use a surfactant when applying SpeedZone Broadleaf Herbicide for Turf and it actually says on the label that adding a surfactant could reduce the selectivity on the turfgrass. Please look at the label for application instructions.
Yes, Turf Nectar AC 15-0-0 with 6% Iron can be mixed with SpeedZone Herbicide following the instructions on each product label.
No, Speedzone Red Herbicide is not labeled for use on Centipede or St. Augustine grass.
A better option would be Speedzone Southern. It is labeled for use on Centipede and St. Augustine grass and treats a lot of the same weeds that Speedzone Red does.
No, SpeedZone Broadleaf Herbicide for Turf - Gallon does not contain a surfactant. The product label does state that adding one may reduce the selectivity on the turfgrass.
It is not necessary to apply a surfactant to SpeedZone Red Herbicide to eliminate wild violet. It could reduce the selectivity of your turfgrass per the manufacturer.
SpeedZone Red is not labeled to be used in any areas where animals graze so we would not recommend it be used in these areas. We do carry several Range & Pasture products by VPG that would be better options. Otherwise we recommend that you contact your local agricultural department and request more information on what can be used on the type of grass you have in your pasture.
SpeedZone Broadleaf Herbicide for Turf could burn St. Augustine and is not labeled for application to it. Blindside would be the best producf to use.