Quizalofop and Sethoxydim Activity as Affected by Adjuvants and Ammonium Fertilizers

Abstract

Ammonium fertilizers, petroleum oil concentrate, and nonionic surfactant were evaluated as postemergence spray additives to improve giant foxtail and volunteer corn control by 28 g ai ha−1of the ethyl ester of quizalofop or 56 g ha−1sethoxydim. Additions of 0.25% by vol nonionic surfactant or 2.5% petroleum oil concentrate improved grass control, but additions of 10% urea ammonium nitrate (28-0-0), 10% ammonium polyphosphate (10-34-0), or 0.1M ammonium sulfate (21-0-0-24S) did not consistently affect grass control. In laboratory studies with corn, greatest14C absorption from leaf-applied14C-quizalofop (8 h after treatment) was found with additions of petroleum oil concentrate (80% absorbed) or nonionic surfactant (18% absorbed), while less absorption was observed with treatments containing either no additive, urea ammonium nitrate, ammonium polyphosphate, or ammonium sulfate (8 to 13% absorbed). Surface tension and droplet size of spray solutions were affected primarily by additions of nonionic surfactant, petroleum oil concentrate, and the formulated herbicides. Solution density, solute potential, pH, and buffering capacity were primarily affected by fertilizer additions.