Tuesday, August 20, 2019

Herbicide reboot may be needed if spraying with hard water

March 5, 2019 by  
Filed under Crops

Farmers destroying weed-infested stubbles or old grassland prior to planting spring crops, including maize, may need to boost glyphosate performance if farming in hard water areas.

Crop destruction before planting performs several important functions says Hall Charlton, of agronomy firm ProCam – including controlling weeds and removing the “green bridge” of living plants that can carry diseases and pests from one crop to the next.

But the withdrawal of ethoxylated tallow amine from glyphosate formulations – previously included as a leaf wetting agent to enhance activity – could see reduced performance with some treatments this year, he suggests.

If hard water is used for spraying, this could also further compromise the level of herbicide performance, warns Mr Charlton, unless steps are taken to regain it.

“Hard water, whether from the mains or a borehole, is a key factor that can hold back glyphosate performance,” he explains. “The calcium in hard water binds to some of the glyphosate, rendering it less active.

“You should know if you have hard water. But even so, it could be worth getting water tested. If hard water is a concern, it may be worth adding a water conditioner to the spray tank. These treatments effectively mop up the calcium so it can’t bind to the glyphosate so that more of it is biologically available.”

Water conditioners

That said, there are various types of water conditioners available – so it’s worth checking you are using the correct type, says Mr Charlton. Some also include buffering agents to adjust the pH of the spray liquid in favour of improved uptake by the leaf, he notes.

RoundUp manufacturer Monsanto says 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.

High levels

It says most UK water contains 1-10 ppm of iron which poses no threat to Roundup. However at high levels, usually above 20 ppm, poor performance can result as oxides of this metal can lock up glyphosate.

Monsanto says in all cases where a water quality issue is diagnosed, the problem can be overcome by the addition of a proprietary water conditioner.