Atrazine not causing groundwater pollution

COLUMBUS – A Midwestern study, part of which was done in Ohio, showed that properly applied atrazine shouldn’t threaten groundwater supplies.

In fact, researchers were hard-pressed to find any atrazine outside of the 6-inch soil depth zone, after taking 12,000 water samples.

“We didn’t recommend any substantial changes for using atrazine based on our data,” said Norm Fausey, research leader for the USDA’s Soil Drainage Research Unit based at Ohio State University.

“Atrazine is an effective herbicide and easy to use, and properly used, it’s not causing groundwater pollution.”

Soil makes difference.

Atrazine’s effect on surface water is another question.

Part of the national data came from Missouri, where runoff was rampant off the watershed’s impermeable claypan soils. Atrazine levels in spring were recorded at peaks above 1,000 parts per billion (ppb), compared to below 3 ppb in late summer. Farm management projects were unsuccessful in reducing runoff levels.

The Missouri study recommended reduced herbicide use to eliminate potential for runoff during peak months.

On the surface.

Although not involved in the study, water from surface sources such as Hoover Reservoir, which supplies Columbus, Ohio, is occasionally treated for atrazine levels exceeding allowable standards.

Treatments involving charcoal filtering are expensive and can daunt limited budgets, especially for smaller water treatment systems, said Mark Loux, OSU weed specialist.

“You get spikes in atrazine levels in late spring or early summer, but for the rest of the year, it’ll be down to below allowable levels,” Loux said.

The Ohio portion of the federal study was done from 1991-96 at OSU’s Management Systems Evaluation Area near Piketon, where a shallow aquifer under the well-drained farmlands would theoretically be vulnerable to atrazine seepage and easily detectable.

The Ohio site showed the least movement of atrazine compared to sites in the other seven cooperative states.

The exception to the Ohio findings occurred in states with expanses of sandy soils like Wisconsin and Minnesota, where atrazine is more mobile and likely to infiltrate into groundwater, Fausey said.

Ohio’s agricultural sands are in northern parts of the state, and usually on knolls and spotty flats not extensively row cropped as other soils.

Since the public became concerned about drinking water contamination, the government reduced application rates for atrazine, said Jeff Stachler, OSU research associate and weed specialist. Consequently, some weeds escape control at the weaker rates.

The lowered application rates may be why the Ohio MSEA didn’t find groundwater pollution, Fausey said.

Cultural practices are another factor. In continuous corn, atrazine likely is used every year and fed to soil microbes, rendering it harmless to the environment. In crop rotations, atrazine would be used only when corn is planted, reducing the long-term amount applied to those fields compared to continuous corn. In a corn-soybean rotation, it would be applied every other year; in a corn-soybean-wheat situation, every three years.

Atrazine applications usually are restricted to 50 feet from wells, abandoned wells, streams, rivers and bodies of water. Special procedures must be followed when applying to tile-terraced fields containing standpipes.