Along with the Roundup Ultra and 2,4-D, Wassenaar includes ammonium sulfate. The Central Iowa farmer says ammonium sulfate is used to soften the water and get better action on Roundup. Ammonium sulfate seems to get it into the plant quicker,'' Wassenaar says. Choosing the correct adjuvant is important with reduced-rate herbicides which have active ingredients of an ounce or less, says Tim Chicoine, corn product development manager with DuPont Agricultural Products in Indianapolis. With systemic herbicides Accent, Synchrony, Reliant, Basis and Pursuit it's important to cover the leaf, he says.
Adjuvants affect how herbicides stick to plants or cut through waxy leaf surfaces or both.
Adjuvant choices aren't as critical with soil-applied herbicides that have active ingredients of a pound or more, Chicoine says, such as Extrazine or Bladex. The right adjuvant selection can make or break you,'' he says. To simplify the selection pro cess, DuPont and American Cyanamid list adjuvants to be used with their herbicides, Chicoine notes. The herbicide's mode of action affects the adjuvant selected, he says. A surfactant reduces the surface tension of a spray droplet on a leaf surface, improving its retention, says Mike Dietrich, technical service representative with American Cyanamid in Indianola.