Chaff Lining Shows Major Resistant Weed Control Promise in Iowa Field Trials
The bare-bones simplicity of chaff lining may provide farmers with resistant weed control for pennies on the dollar. Funneling soybean chaff and its weed seed contents out of a combine into concentrated lanes is a non-chemical, inexpensive means to control weeds—particularly waterhemp, the bane of many Midwest farmers—and chaff lining is showing major promise in ongoing Iowa field trials.
With farm shop production of a chute and baffle, along with a DIY helping of elbow grease, a grower can build the basic physical components of a low-cost system to directly attack weed seed proliferation. “The chaff lining concept is simple,” says Prashant Jha, an Extension weed scientist at Iowa State University who conducted the first-ever chaff line trials in U.S. soybean production.
Intriguing Data
Chaff lining is a Harvest Weed Seed Control (HWSC) method already widely adopted in Australia, typically in wheat fields. (HWSC is a preemptive attack on the soil seed bank through one or more non-chemical techniques: chaff lines, chaff carts, narrow-windrow burning, and high-impact seed mills.)
A baffle is utilized to separate straw from chaff, and a chute is connected to a combine’s rear. As a combine operates, chaff-containing weed seed, is expelled in narrow bands. The initial purpose of the baffle and chute is not to kill weed seed, but rather to concentrate it within defined locations and prevent spread across a field.
Jha’s Iowa field data suggests more than 95% of waterhemp seed is deposited within the chaff lines at the time of soybean harvest. “It’s a very simple and low-cost system,” Jha explains. “For our testing, we spent roughly $7,000, including shipping, to order a chaff lining kit from Australia. That’s extremely low cost when you consider a seed mill might cost $70,000 or more.”
However, chaff lining equipment costs can go even lower, Jha continues. “If a grower chooses, the chute and baffle are something that easily can be made on-farm. It’s a simple design and simple engineering.”
With research funded by the Iowa Soybean Association, Jha ran a chaff line unit on soybean fields in 2020 and 2021, depositing 18”-20” wide strips, each with 6”-8” depth at the time of harvest. Of weed seed entering the combine, he recorded more than 95% retention of weed seed within the chaff lines that entered the combine, including waterhemp.
The freshly laid chaff ribbons, chock full of weed seed, remained in place after harvest was complete. In spring 2021, the lines revealed intriguing data on seed viability, and Jha’s trials paid big dividends for the future of resistant weed control.
Herbicide Costs Drop
In 2021, Jha planted corn and soybeans directly atop the deposited chaff lines. (Significantly, he noted minimal disturbance of the lines over winter and inconsequential wind movement.) “We used banded versus broadcasted application of herbicides pre and post, and overall, we saw 70-75% more waterhemp appear on the chaff lines compared to outside the chaff lines—but that was what we expected.”
However, waterhemp emergence in the chaff lines was delayed by two to three weeks as a result of the residue effect, a major detail related to chemical sprays. “For example, when we applied a corn herbicide application post, we were dealing with smaller size waterhemp of 3”-4” versus 6”-10”. It’s definitely a very good strategy, because the delay means you are dealing with a smaller size weed which greatly enhances the efficacy of the post application. One pre application of Acuron fb Liberty and Halex GT in LibertyLink corn provided season-long control of waterhemp on the chaff line.”
Outside the chaff lines, the presence of waterhemp was dramatically reduced, according to Jha. “No question: the chaff lines reduced our herbicide use overall. Outside the lines, weed presence was greatly diminished, and we were good with just one pre application of Acuron. I’d estimate we saw more than 95% reduction of the spread of weed seed on a per acre basis.”
Once weed seed is within the moisture of the chaff lines, Jha says to expect natural death and fungal decay of seed. Jha recorded several thousand waterhemp seeds per square foot within the chaff lines, but observed “nowhere near that emergence” the following spring. “That’s an environment where you’ve enhanced predation and microbial decay on weed seed.”
Jason Norsworthy, a University of Arkansas weed scientist, has been at the forefront of Harvest Weed Seed Control in the U.S. for the past decade. “Chaff lines have high moisture content during winter and the weed seed has a tendency to rot,” details Norsworthy. “Emergence happens later as well, and in the South, you can plant soybeans and if the pigweed comes up late enough, there is a good chance the beans will have canopied by that time. We’re getting ready to initiate some chaff line trials and we’ll include cover crops as a component in the 2022 growing season.”
Long-term, Jha estimates that an 18”-20” band of chaff can provide a major reduction in herbicide costs. “First, a grower’s chemical expense can go down,” he says. “Second, there will be a reduction in the spread of resistant weed seed because it’s all concentrated and managed within the band. Projected over multiple years on a per acre basis, herbicide costs are going to drop.”
Drain the Bank
In the near-future, Jha sees big acreage farmers adopting seed mill technology, and smaller acreage farmers leaning toward chaff lining. “It’s related to expenses and how much you want to pay,” he says. “You can’t get much more low-cost than chaff lining, but it appears to be effective. Even some organic farmers will be interested in chaff lining.”
Jha has expanded chaff line trials in 2022 and will collect data in corn and soybeans from two chute/baffle units. He recently wrote and received approval on a USDA grant for research on chaff lining and seed mill (Redekop) operation in Arkansas, Iowa, and Kansas. Jha already has collected seed mill data in central Iowa in 2020 and 2021, and reports more than 90% seed kill of waterhemp and no combine-plugging issues. “The Redekop seed mill showed very positive results in 2020, our first year to use it. It’s only 40 horsepower and was very efficient,” he says. “Ways to reduce the header loss of waterhemp seeds, which could be as high as 33%, need to be further investigated to make the technology more efficient in reducing weed seed banks,” Jha adds.
“The seed mill results look very good, but chaff lining can bring the same type of results long-term. Used for three or four years in succession, chaff lining could result in a dramatic decrease in weed presence.”
What does Jha believe is the best course for chaff line management? “We’re finding out the details and have plenty of questions left to answer,” he concludes. “Some farmers may want to put a high rate of herbicide directly on the chaff line. I think chaff lines are a management tool that is site-specific, but the overall purpose will be the same: Exhaust the soil seed bank year by year.”
To read more stories from Chris Bennett (cbennett@farmjournal.com — 662-592-1106), see:
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