Atrazine has been around since 1958 and is currently the most used pesticide in U.S. agriculture, according to Monty Dozier, a Texas Extension Water Resources Specialist. Extensive use led to detection of atrazine in both surface and groundwater and a special review by the Environmental Protection Agency. One result of the special review is a new interim re-registration eligibility decision (IRED) by EPA.
“Re-registration requires a more concentrated effort of monitoring surface waters designated for public consumption in watersheds where atrazine is used. Included in these watersheds are eight designated as highly vulnerable because of prior atrazine concentration levels at levels significantly higher than acceptable as set forth by the EPA,” Dozier said.
“Under the IRED, future atrazine use will be banned if required mitigation steps do not reduce atrazine concentrations to acceptable levels.”
Dozier says no target watersheds have been identified in Texas. But several located mainly in the Central Texas Blacklands are listed as vulnerable.
“In vulnerable watersheds, atrazine concentrations have approached or exceeded (at a less significant level) acceptable atrazine levels. Vulnerable versus highly vulnerable is similar to a severe weather watch versus a severe weather warning,” Dozier says.
He says in vulnerable watersheds atrazine use would be banned only after exceeding acceptable levels, mitigation strategies are implemented and levels do not come down to acceptable.
Ongoing research at the Stiles Farm near Thrall compares atrazine application methods to identify best management practices. Studies include: traditional broadcast surface-applied method, a 13-inch banding application followed by an early season cultivation and a broadcast application followed by immediate mechanical incorporation of atrazine into the top 2 to 3 inches of soil.
Banding applications instead of broadcasting reduces the risk of runoff, Dozier says.
All three systems provided good weed control. But the BMP practices significantly reduced the amount of herbicide lost to runoff. Control was off by 7 percent in the banded treatment. “But we saw no yield reduction,” Dozier says.
The research project was a joint effort of Texas Cooperative Extension, Texas Agricultural Experiment Station, the USDA-Natural Resources Conservation Service, the Texas Corn Producers Board, and the Texas Department of Agriculture.
Dozier presented the findings at the recent Stiles Farm Field Day. The farm, located near, Thrall, is a Texas Agricultural Research Center.