Research And Demonstration Plots Balance Runoff And Erosion Reduction
COLUMBIA, MO.
Collaboration between University of Missouri
Extension and the USDA 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.
The harrow decreases the 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. About a
decade ago, he 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.
“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 says 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 says 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 farmscale
equipment. Plots were set up using no-till,
the rotary harrow and minimum till with a field
cultivator. 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 says 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.
“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 says 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.” Δ