Publications - Faculty - Recently Submitted Faculty Publications 2008
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Singh - Weed Science
Herbicidal Activity, Absorption and Translocation of Glyphosate on Yellow Nutsedge (Cyperus esculentus L.) as Affected by Zinc
H. F. Abouziena, R. A. Elmergawi, S. Sharma, A. A. Omar, and M. Singh
Abstract. Producers who grow glyphosate-resistance plants may apply a foliar micronutrient solution as tank mixture with glyphosate. Therefore, the interaction between zinc (Zn) as zinc sulphate (ZnSO4) and glyphosate to control yellow nutsedge weed as well as absorption and translocation of 14C-glyphosate were investigated. Application of glyphosate at 850 g a.i./ha produced 90% yellow nutsedge control at 5 wk after treatment (WAT). Addation of Zn at 1,000 ppm to the spray solution completely antagonized the efficacy of glyphosate. Control percent significantly decreased by increasing zinc level in spray solution (500 to 2000 ppm) as compared with check glyphosate. Including zinc at 1,000, 2,000 and 4,000 ppm in glyphosate spray solution completely eliminated the reduction effect of glyphosate on plant height and produced plants with more shoots and tubers per plant than control.. Plants sprayed with 2,000 ppm zinc mixed with 850 g a.i./ha had 25 shoots and 11.3 tubers/plant compared with 1.3 and 1.0 for those of glyphosate alone and 5.3 and 6.7 for untreated control plants. A gradual decrease in amount of 14C-glyphosate uptake and translocation was observed due to increasing zinc level in glyphosate spray solution. Antagonism effect of zinc with glyphosate depended mainly on the reduction of 14C absorption into or translocation within treated tissue. Less than 10% of applied 14C-glyphosate at 850 g a.i./ha was absorbed when mixing glyphosate with either 1,000, 2,000 or 4,000 ppm zinc compared with 85% for glyphosate alone. These treatments inhibited more than 90% of 14C-glyphosate translocation out of the treated leaf and more than 50% of tuber translocation relative to glyphosate check treatment. Among the 14C-glyphosate translocated from treated leaves, a high percentage was presented in yellow nutsedge tuber as a result of zinc treatments. Mixing glyphosate at 1700 g a.i./ha with 4,000 ppm zinc caused a relatively low control , while glyphosate at 2,625 g a.i./ha with zinc to 8,000 ppm produced a complete control of yellow nutsedge 3 WAT. The results indicate that adding Zn at 1,000 ppm had the potential to complete elimination the efficacy of glyphosate on yellow nutsedge, therefore the presence of Zn metal in glyphosate spray solution is not desirable.
