Rotary harrow beats no-till to reduce atrazine runoff
“We thought these students might be able to do some quick assessments of how practical it would be, what kind of residue cover, what kind of working capacity it would have to meet the needs of farmers,” Lerch said. “So we kind of laid the groundwork and gave the students a framework of what we were interested in. If they could assess existing implements and look at the feasibility to see if this was an idea worth pursuing, it would be a huge help for us to decide if this was a research project worth doing.”
Lerch said a group of students did excellent work showing that the rotary harrow was probably the best combination of incorporating atrazine and leaving quite a bit of crop residue. It also has a very high working capacity—a farmer can cover 40 acres an hour—and doesn’t require a huge tractor.
Lerch and Broz took the idea to Syngenta, which Broz said had been under pressure from the Environmental Protection Agency to come up with best-management practices to control atrazine. A proposal was put together based on the students’ findings and Syngenta agreed to fund the research and demonstration project.
The plots, set up at the MU Bradford Research and Extension Center, were large enough for each tillage treatment to be put in with farm-scale equipment. Researchers used a rainfall simulator to create the runoff, which was captured during a 90-minute rain event. The concentration and total load of sediment and atrazine in runoff were measured.
Lerch said the harrow did not significantly increase erosion compared to no-till, whereas under minimum till with a field cultivator, erosion was four to five times higher than no-till. No-till had the highest atrazine concentrations and lost the most total atrazine—22 percent of what was applied. The minimum till, because it incorporates deeply, had the lowest atrazine loss and concentration, and the rotary harrow was in-between.