Rotary harrow beats no-till to reduce atrazine runoff
Collaboration between University of Missouri Extension and the U.S. Agriculture Department’s Agricultural Research Service has shown that using a rotary harrow to incorporate atrazine in the soil balances the amount of runoff and erosion compared to other tillage systems.
In a field size research study of using no-till, a rotary harrow and minimum till with a field cultivator and applying atrazine herbicide, the harrow decreases the atrazine runoff compared to no-till and decreases erosion compared to minimum till use of a field cultivator, said Bob Lerch, a USDA ARS soil scientist and adjunct assistant professor at MU.
In Missouri’s claypan soils, the two biggest water-quality issues are soil erosion and atrazine contamination, Lerch said. This is a main reason the research was done.
In reporting the results, he said, “The bottom line was the harrow really balanced these two concerns,” Lerch said. “We didn’t increase erosion a lot and we significantly decreased atrazine loss. I can say it is the first time I’ve ever done a study where the outcome was what I hoped it would be. It almost never works that way.”
Adoption of these results is the next step. Lerch said the real impact of this is not putting it in a publication somewhere; it is a matter of whether farmers are going to pick this up as a practice that could deal with both the erosion and atrazine issue. He sees the 30 years of promoting no-till as an obstacle to that.
“What I’m saying is don’t till more. I’m saying till differently and till with a purpose,” Lerch said. “Till with the idea that you are going to minimize erosion but you will mix that chemical in just a little bit to keep it out of the waterways. That’s good for the producer because of better weed control and better yields.”
About a decade ago, Lerch and some ARS colleagues discussed the idea of using a tillage implement and/or sprayer combo to incorporate atrazine into the soil while keeping enough crop residue to control erosion.
“So that was kind of the dream,” he said. “Ideally, we would be using some implement that is already out there. We didn’t want to come up with a new implement. We thought there could be something out there on the market that could help solve this problem.”
Due to lack of funding, the idea wasn’t pursued for several years. Then Bob Broz, extension assistant professor at MU, asked Lerch if he had any ideas for a capstone project for agricultural systems management.
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