The effect of dilution water quality on herbicide efficacy
The antagonistic effect of Ca2+ and Mg2+ ions on the efficacy of glyphosate (Roundup) has been well documented for some time but there is relatively little information available on the effect of other ions on glyphosate or other herbicides. Field trials were conducted at Saskatoon in 1989 and 1990 to determine the effect of dilution water ion content on the efficacy of several herbicides. Water sources examined were: Saskatoon (surface, fresh, low mineralization), Goodale (artesian well, hard, high Ca2+ and Mg2+), Zelma (well, hard, high Fe3+), Outlook (well, soft, high Na+), Unity (well, soft, medium HCO3-), Maple Creek (well, soft, high HCO3-) Recommended and less than recommended rates of selected herbicides were applied in four replicate field trials using standard flat fan nozzles that delivered 130 L/ha (1989) or 110 L/ha (1990) of spray mixture. Herbicide X water combinations that have resulted in reduced weed control as compared to Saskatoon water as the check are: glyphosate (Roundup) X Goodale or Zelma, sethoxydim (Poast) X Unity or Maple Creek, clethodim (Select) X Unity or Maple Creek, 2,4-D amine X Goodale, Outlook or Unity. Imazamethabenz (Assert) was not affected initially but plants treated with water from Unity or Maple Creek recovered more rapidly than those treated with Saskatoon water. Fenoxaprop-ethyl (Excel), 2,4-D ester, and glufosinate ammonium (Ignite, Harvest) were not affected by water source.
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