Nitrogen Fertilizer, Oil, and Surfactant Adjuvants with Nicosulfuron

Abstract

Urea and ammonium nitrate are components of 28% nitrogen liquid fertilizer (UAN) that is often used as an adjuvant in addition to surfactants or oils with herbicides. Ammonium nitrate and/or UAN fertilizer enhancement of nicosulfuron phytotoxicity to large crabgrass or yellow foxtail depended upon the associated oil or surfactant adjuvant. Ammonium nitrate reduced the effectiveness of most block copolymers but not other surfactants with nicosulfuron for large crabgrass. Urea never enhanced and often reduced surfactant and oil adjuvant enhancement of nicosulfuron. Ammonium nitrate or UAN, but not urea, enhanced nicosulfuron phytotoxicity to yellow foxtail when the spray carrier contained sodium bicarbonate. These research results indicated that enhancement of nicosulfuron efficacy from UAN is mainly from the ammonium nitrate component. However, the benefit to nicosulfuron from UAN or ammonium nitrate depended upon the associated surfactant or oil adjuvants.