URAN® (28-0-0) as an additive for reducing sodium bicarbonate antagonism of cyclohexanedione herbicides

Abstract

Field tests were conducted in 1990 and 1991, to evaluate the potential of 28-0-0, (a mixture of ammonium nitrate and urea), as an additive when using sodium bicarbonate water for the dilution of cyclohexanedione herbicides. In 1990, water from: Saskatoon (surface, low bicarbonate), Unity (well, 675 ppm bicarbonate), and Maple Creek (well, 956 ppm bicarbonate), were mixed with the 0.5X and 1X rates of sethoxydim and clethodim. These combinations were tested with and without 28-0-0 at 2.3 L/ha. Unity and Maple Creek water reduced the efficacy of both herbicides. The addition of 28-0-0 overcame this antagonism in all treatments at the 1X rates of herbicide, and resulted in better control in most treatments at the 0.5X herbicide rates. The use of 28-0-0 also increased the efficacy of sethoxydim in Saskatoon water, where antagonism was not a factor. In 1991 three rates of 28-0-0 (1.15, 2.3, and 3.45 L/ha), and 4 L/ha of ammonium sulphate, were tested with the 1X rates of tralkoxydim and a high concentration formulation of sethoxydim. Medium and high concentration sodium bicarbonate water was prepared by adding sodium bicarbonate to distilled water. The bicarbonate waters reduced the efficacy of tralkoxydim, while no antagonism of sethoxydim was found, suggesting that the high concentration formulation of sethoxydim may not be as sensitive to the presence of sodium bicarbonate as the original formulation. All additives increased the efficacy of both herbicides, but no differences were found between the effect of ammonium sulphate or any rate of 28-0-0.