Ammonium Sulfate Enhancement of Glyphosate and SC-0224 Control of Johnsongrass (<i>Sorghum halepense</i>)

Abstract

Ammonium sulfate enhanced the initial control of johnsongrass by glyphosate and SC-0224 applied in the fall or summer. Glyphosate at 0.42 kg ha -1 in combination with ammonium sulfate at 3.33 kg ha -1 provided levels of fall johnsongrass control and spring regrowth control comparable to glyphosate at 0.84 kg ha -1 . Spring applications to mixed populations of seedling and rhizome johnsongrass showed that ammonium sulfate added to glyphosate or SC-0224 afforded little enhancement of herbicide efficacy. Glyphosate or SC-0024 at 0.42 kg ha -1 applied in combination with logarithmically decreasing rates of ammonium sulfate demonstrated reduced weed control with ammonium sulfate rates above 9.7 kg ha -1 .