The role of surfactants and crop oil concentrates is to improve retention on the leaf surface and increase movement of the herbicide from the leaf surface into the leaf. The purpose of AMS is considerable different than traditional additives, but under many situations can be just as important. When the product is in the herbicide jug the negatively charged glyphosate molecule stays closely associated with the positively charged salt. However, once the herbicide is added to the spray tank with water things can happen that may reduce the performance of glyphosate. All water sources contain salts such as calcium, magnesium and others.
Water hardness is a rating of how much salt is present in the water.
Research has shown that calcium and magensium salts commonly found in water reduce the activity of glyphosate. These salts interact with charged portions of the glyphosate molecule to form complexes that are not absorbed as quickly by plants as other salts of glyphosate. Two mechanisms have been proposed for the beneficial effects of AMS used with glyphosate products. These crystals were not present when AMS was not included in the spray solution. The authors speculated that the sulfate ion in AMS combines with calcium to form calcium sulfate crystals, therefore preventing the formation of the calcium-glyphosate complexes.