LETHBRIDGE, Alta. – While much has been made of how water can carry farm chemicals away from their intended targets, recent studies point to another culprit.
A Lethbridge study shows up to six percent of herbicides can be whisked away by wind.
Frank Larney, a soil scientist at Agriculture Canada’s Lethbridge Research Centre, said his studies show wind can play a greater role than water in carrying expensive and often harmful chemicals away from intended crops.
“People thought that water erosion of herbicides was an issue. Up to 30 times as much herbicide can be moved to non-target areas by wind,” said Larney.
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Past studies have shown that 0.2 to one percent of herbicide can be carried away by water.
The herbicides that miss their targets can drift to nearby fields and damage susceptible crops, or end up in dugouts or waterways, or inhaled by people in nearby communities.
Larney’s study, in wind-harried southwestern Alberta, showed an average of 4.5 percent of surface-applied herbicides wound up in topsoil that had been carried away from the target field by wind.
Losses lower
By contrast soil-incorporated herbicides lost only 1.4 percent of the original application.
Six herbicides were tested. A mixture of diclofop and bromoxynil (Hoe-Grass II) from the soil ended up off target more than the other five with 6.5 percent of the product lost.
A Saskatchewan study at the Outlook irrigation research facility showed that diclofop losses due to water runoff were only 0.2 percent.
In the wind-loss study, Mecoprop and
2,4-D were carried off target about four percent of the time and trifluralin (Treflan) and triallate (Avadex BW) showed between one and two percent losses.
Most of the soil and herbicide mixture carried by wind traveled only short distances. Some soil was kept from blowing away by standing stubble or other natural wind breaks. Lighter mixtures were more easily carried away.
“The lighter products could travel hundreds of kilometres away under the right conditions,” said Larney.
“Too much tillage is the cause of much of wind erosion. By moving to minimum and zero tillage systems there is much less chance of wind erosion becoming an issue.”
In recent years, moist weather has kept wind-caused soil erosion issues on the research back burner. But when combined with water erosion and evaporation during spray operations, producers could end up with large quantities of pesticides in the wrong place at the wrong time.
Winds died down
In addition to higher than average moisture, a study of wind speeds in southern Alberta has showed lower than average readings for the past six years.
“When you’ve got dust blowing around the environment, that will make a natural pathway for herbicides into the air and into waterways. It creates the potential for problems like herbicides in drinking water or having people breathing in the dust that is carrying herbicides,” said Larney.
Urban centres in Washington state have helped to fund research to address problems caused by wind-borne herbicides in the east-central region of the state.
There’s been no similar flow of research cash in Western Canada and Larney’s study will not likely be repeated in the near future, said the researcher.
“The issue needs more research but in the meantime there is a solution. Stop the erosion before it starts.”
