The Daily Dirt

Auburn Mechanical Engineer Students Meet Ag Needs

This year, a cross disciplinary collaboration that encompassed students and professionals alike has resulted in a solution for a practical agricultural problem. This partnership began in January, when nearly 60 senior mechanical engineering students of Auburn University’s College of Engineerings gathered to listen to speakers from various industries discuss needs, problems, and projects within their given trade. Each presentation represented a possible senior project for the students based on their interests.


Carroll Johnson, USDA-ARS research agronomist

Among the mostly biomedical professionals making presentations was Carroll Johnson, a research agronomist with USDA-ARS, and Dan Evarts, a research technician with USDA-ARS. Johnson and Evarts gave a seminar presentation on research they had been conducting using peanut diggers as a form of weed control, primarily for nutsedge in organic transition systems.

In organic agriculture, weed management is a major obstacle because the majority of chemical herbicides used to control weeds in conventional systems aren’t approved for organic use. Nutsedge is especially problematic, as it is a perennial weed that grows from underground tubers. As long as tubers remain in the soil, nutsedge remains a pest for farmers. The key, Johnson believes, is being able to remove the nutsedge from the field after digging it up with the peanut digger, an implement traditionally used to harvest peanuts by excavating the plants and laying them on top of the soil.

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A nutsedge plant. The tuber is circled.

In previous research, the peanut digger successfully dug nutsedge plants and tubers, but manual labor was needed to physically remove displaced weeds from the fields. Otherwise, nutsedge could survive- particularly if it rained shortly afterwards. This type of labor is extremely costly and time consuming. Johnson shared these observations with Dr. Thomas Way, an agricultural engineer with USDA-ARS in the National Soil Dynamics Laboratory on Auburn University’s campus.

“I asked [Way] if he had any ideas and he said ‘Let me think about it,’” Johnson said. “A couple of months later he got back with me and said ‘I got an idea, how would you feel about that being a senior class project in mechanical engineering?’”

Developing the Concept
Johnson’s presentation to the senior class was met with enthusiasm. Ten students elected to work on the project, a number so large that the group was divided into two teams. Dr. David Beale, a professor in the department of mechanical engineering at Auburn, was the faculty advisor for the project. He, along with Johnson, Way, and Evarts, provided support for the students by offering ideas and answering questions. None of the students working on the project had any background in agriculture, but were quick to understand the practical agricultural need.


“I’m not an engineer, but I knew what I wanted,” Johnson said. “And if I sensed [the students] were missing something, I’d mention it to them, but it really wasn’t necessary. They had a good grasp of the big picture. (…) We did not have to reel them in from some sort of a wild tangent. They knew exactly what they were going to do.”

Throughout the spring semester, the two teams developed different proposals for modifications to a peanut digger that would allow nutsedge to be collected and removed from the field. However, ultimately only one proposal was constructed.

“At the end of the spring semester,” Johnson explained, “[Each team] made a presentation and a prospectus with a detailed budget, CAD drawings, list of materials, and all sorts of calculations on the stresses placed on various points of the prototype. These are the services a professional engineer would provide. We chose the best concept and then the two teams were merged into one.”


The combined team then began construction on the modifications to the peanut digger. The work was done in Way’s lab on Auburn’s campus under his supervision. The peanut digger was a rusty, forgotten piece of machinery found grown-over in the woods, and the transformation was undoubtedly impressive.

A cart attached to the rear of the original peanut digger collects weeds from the spokes as it passes through the field. When the cart is full, it can be taken from the field where the cart hydraulically opens at the back, tilts, and a conveyer rolls the plant material out of the cart. The implement is meant to be used in fallow land, with the goal of decreasing weed pressure before planting crops. Johnson plans to use this modified peanut digger in future research on weed control in transitional organic land to determine how effective it is in removing nutsedge tubers from the field.

“If [land] is in organic transition and nutsedge is problematic, then this is the thing [farmers] could use before they start transition to get it cleaned up,” Johnson said “Then by the time they get to be certified organic, the nutsedge is beat into submission.”

Although transitional organic land will be the bulk of Johnson’s research, the peanut digger can also be used in fields between seasonal plantings as a method of weed control. This will be especially beneficial to organic operations, as there is currently no effective way to deal with nutsedge.

Inaugural Field Test
On July 28, the modified peanut digger was moved from its home at Auburn University to University of Georgia Ponder Farm in Tifton, where Johnson conducts his research. During the field test, Johnson observed that the cart needed to be moved closer to the digger to catch more of the plant material. The students quickly and efficiently determined the best way to do this, which required swapping the location of the peanut digger wheels and the cart hitch, then the conveyer chain on the digger. The students also made additional adjustments in field once the demonstration began.


“I think on a project like this there’s got to be a reasonable level expectation for a prototype,” Johnson explained to the students during the field test. “For me the concept is proven. These are actually, I think, pretty little things. (…) That’s something y’all might have to take into account professionally is reasonable level of expectation for the prototype. Especially when there’s really nothing to go by. Y’all picked a tough project as far as I was concerned. One of the things that impressed me was we saw the problem on this end and y’all saw what the solution probably would be, and we just stood back and y’all did it. That’s what a team is supposed to do. And those who’ve got jobs on the table, you’re going to be part of a team, a team of engineers. Everybody’s got their strength.”

The success of the prototype is promising for Johnson’s research purposes and for farmers, both conventional and organic, dealing with nutsedge since it physically removes nutsedge from the field. It is also good news for the students who worked on it, as they will soon be graduates of the College of Engineering.

“This is an experience they’re going to carry forward as professional engineers,” Johnson said. “They had a client, the client had a need, they made a proposal, a very detailed proposal, they designed it, and they built it. And that’s the way it is in the real world.”_MG_0116

Collaborating Auburn University Mechanical Engineering Students, Class of 2014

David Bandy
Kyle Craig
Jeremy Gillen
Conner Moore
Austin Hussong
Charles Marchman
Spencer Martin
Hunter Robbins
Charlie Walker
Ian White


Check out a video of the modified peanut digger in action here!


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