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Water Quality
Hard water containing Calcium and Magnesium salts or water rich in Iron can reduce efficacy of glyphosate, especially with sub-optimum dose rates, in high water volumes and where the ion content is high.
Iron
Normal UK water contains 1-5 PPM of Iron which poses no threat to Roundup. However at high levels above 5 -10 PPM poor performance can result as oxides of this metal lock up glyphosate. Boreholes and artesian wells may contain iron derived from surrounding sandstone, rusting metal bowsers can also cause problems if water is left standing in them.
Hard Water
Normal UK water contains 1-5 PPM of Iron which poses no threat to Roundup. However at high levels above 5 -10 PPM poor performance can result as oxides of this metal lock up glyphosate. Boreholes and artesian wells may contain iron derived from surrounding sandstone, rusting metal bowsers can also cause problems if water is left standing in them.
Hard Water
Chelation
In hard water chelating cations of Ca ²+ or Mg ²+ can bind to the glyphosate rendering it biologically inactive and reducing the herbicidal effect of the diluted spray solution
Hardness is a measure of Calcium, Magnesium and Manganese salts and is expressed either as degree of hardness
or as parts per million of Calcium Carbonate, (Ca CO3).
One degree of
hardness is 17.9 ppm Ca CO3Soft water has less than 200 PPM Ca CO3
Medium water has 200-400 PPM Ca CO3
Hard water has more than 500 PPM Ca CO3
Normal mains water has a hardness in the range of 100-400 PPM. In calcareous areas, bore holes and artesian wells may contain levels up to 1,000 PPM. They may also contain Iron from sandstone or high organic matter/ acid levels from springs, bogs and moors.
Hard water has more than 500 PPM Ca CO3
Normal mains water has a hardness in the range of 100-400 PPM. In calcareous areas, bore holes and artesian wells may contain levels up to 1,000 PPM. They may also contain Iron from sandstone or high organic matter/ acid levels from springs, bogs and moors.
Kits are available to test on farm supplies by simple titration, but local water companies are obliged to give out a detailed analysis of mains water to customers on request.
The Effects of water quality and rate on efficacy of glyphosate on volunteer cereals
In general at levels in excess of 500 PPM there will be a decrease in glyphosate activity, but it may only be noticable at low rates. At levels greater than 1,000 PPM overall performance of glyphosate may be variable, particularly on perennial weeds, or with sub-label dose rates.
pH
Acidifying surfactants claim to boost efficacy and minimise hydrolysis of glyphosate, but Monanto trials showed no impact in performance of Roundup using water between pH 4 and 8. The ideal pH for performance of glyphosate is between 4 and 5.
Neutralising with Ammonium sulphate
Neutralising with Ammonium sulphate
In all cases where a water quality issue is diagnosed, the problem can be overcome by the addition of a proprietary water conditioner.
Typically hard water and high pH occur together but the combination is not significantly greater than the individual factors, with hardness being the most significant.
