Production Blog
Pam Smith DTN\Progressive Farmer Crops Technology Editor

Thursday 11/07/13

Bringing in the Weed Seeds

KEISER, Ark. (DTN) -- The Palmer amaranth (pigweed) plant stood a good six feet tall, despite its heavy seed load. This time of year, female pigweed plants appear Medusa-like -- each branch a twisted, ugly dread lock filled with seed. Each plant represents the potential of an estimated half million to one million more plants next year if not controlled.

Palmer amaranth looks on as Arkansas scientists try chaff carts to capture the renegade weed. Chemical controls are becoming less reliable on this yield robber. (DTN photo by Pamela Smith)

It's that vile seed that Jason Norsworthy wants to extract from the seedbank before it ever makes a deposit. It's why the University of Arkansas weed scientist put a chaff cart to work in an Arkansas soybean field this fall.

Based on a concept used in Australia, a silage wagon-like cart towed behind the combine collects the soybean residue that exits the machine following seed separation. The idea is to mechanically capture the weed seed rather than scatter it across the landscape. Eventually, piles of chaff are burned to destroy the seed.

I arrived as the combine and chaff cart was making some of the first rounds through a pigweed-infested field. "We don't typically trailer equipment behind combines in this country," said Norsworthy, explaining that getting the cart hitched properly had caused delays.

The cart is experimental. It's a prototype based on a picture Norsworthy brought home after visiting Australia earlier this year. During these first efforts on American soil, all the soybean chaff leaving the combine is dumped onto a conveyor and elevated into the cart. A sloped cart floor causes the material to slide to the bottom and when full, a hydraulic door at the rear of the cart lifts and deposits the soybean and weed waste into piles to be burned.

Built by a local welding shop, the chaff cart reminded me of a black Amish buggy with a slow-moving vehicle sign plastered on the back. Slow moving will undoubtedly be the first complaint if this system gets implemented on American farms. Feeding all this material into the chaff cart takes time. Things get choked up.

Still, Norsworthy said his first trials with the cart appear to be gathering 90% of the weed seed. "We've got to do something beyond looking to a jug for answers to herbicide-resistant Palmer," he said. "I have growers spending $80 and more per acre just to control this weed. We have hoe crews in the field hand weeding. I think we have to explore every option we can."

University of Western Australia weed scientist Michael Walsh traveled to Arkansas to help Norsworthy get the equipment up and running. Australian farmers are aggressively using chaff carts and other mechanical seedbank management solutions to manage herbicide-resistant ryegrass and wild radish in wheat.

Norsworthy said his research shows 99% of Palmer amaranth retains its seed until harvest and shattering is not an issue. What could be problematic is Palmer does have multiple flushes throughout the year.

Still, Norsworthy said, it's those big, mature Palmer amaranth plants in the fall that really set the stage for the coming year. Southern growers have come to realize that keeping Palmer amaranth in check means year-long management.

That's a lesson farmers in other parts of the country will likely get to sample if they don't take this weed seriously. In total, herbicide-resistant Palmer amaranth has been confirmed in 24 states, from Arkansas to Michigan to California.

The presence of Palmer amaranth was recently identified in Iowa in Harrison County near the Missouri River. Weed scientists in Illinois, Indiana, and Michigan report the weed is spreading in their states. Although every Palmer amaranth plant isn't resistant, this weed has already shown an ability to adapt faster than farmers can react.

The simplest and most cost-efficient manner of managing Palmer amaranth, or any new weed species, is early detection and eradication before a permanent infestation is established. Found early, plants can be removed from the field before seed production establishes a permanent seedbank and becomes a persistent problem.

That's easier said than done. Every Arkansas farmer struggling with Palmer amaranth today will tell you what they wish they'd done yesterday. The question is will Midwest growers be willing to spend the money and adopt the strategies that allow them to avoid putting the cart behind the combine?


Posted at 2:17PM CST 11/07/13 by Pam Smith
Comments (7)
when I was young we had a scour clean on the combine to catch the weed seeds. back to the good old days!
Posted by BRIAN BERGER at 9:41AM CST 11/08/13
Brian--that's an interesting point. You've gone past my knowledge of current combine technology. Do we not still have this feature? You've got my attention and curiosity up!
Posted by Pamela Smith at 9:44AM CST 11/12/13
Instead of collecting the seeds and messing with burning piles, couldn't you simply install some kind of a roller mill or grinder to render the seeds nonviable than scatter the shredded seeds evenly.
Posted by Vince Moye at 6:31AM CST 11/14/13
Vince--they are doing that in Australia. It is called the Harrington Seed Destructor. At this time, it is also a machine that pulls behind the combine, but the engineering is close to incorporating it into the machine. Of course, this adds weight and more power requirements to the combine (not to mention cost), but it is working there in wheat with the main weed problem being Lolium--ryegrass. My point in writing this story wasn't as much to say that chaff carts are the answer as to point out the necessity to control this weed before it gets a foothold--if you are in an area to do so.
Posted by Pamela Smith at 11:23AM CST 11/14/13
Pamela: Read your interesting article in DTN Grains Edition regarding Palmer Amaranth. As a farmer in western Kansas, we have a major problem with this weed and are extremely interested in the research to chemically eradicate this pest. We are having to give up no-till and put tillage equipment back in the field to solve our problem. Would appreciate any news that you may have on this effort. Regards Jack Miller
Posted by Cheri Zagurski at 1:50PM CST 11/14/13
Burning? That will make the Environmentalist' happy.
Posted by Bonnie Dukowitz at 6:26AM CST 12/12/13
Bonnie--it's a good point. In Australia, they've also had some problems with fires getting away from them. They've tried baling chaff and recycling it through livestock or using it in other ways, but in the case of pigweed, I'm pretty sure some of the seed would pass through the livestock.
Posted by Pamela Smith at 8:34AM CST 12/21/13
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