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New tool for fighting herbicide-resistant weeds

Most farmers are aware of the concept of “air seeding;” i.e, distributing wheat or rice or bermudagrass seed with an airplane or a spreader truck or even by hand.

What some may not think about is another method of air seeding, spreading seed, especially of glyphosate or other herbicide-resistant weeds like Palmer amaranth, out the back of their combine during harvest operations.

Australian producers, who have been fighting herbicide-resistant as long or longer than their American counterparts, have been thinking about the concept and have developed some tools to prevent the random distribution of weed seed.

One of those is the chaff cart, a large, “boll-buggy” type implement, which Jason Norsworthy, a professor of weed science at the University of Arkansas, had on display at the Respect the Rotation Pigposium at the Northeast Research and Extension Center July 23. Norsworthy had the implement built in Fayetteville in 2013.

“We’ve done some work on Palmer amaranth where we found that about 99 percent of the pigweed seed that is harvested during the combining operation actually goes into the combine, and a good portion of that is going to exit the combine and be spread back on to the field,” he said.

“The idea of the chaff cart from the Australians is they use the cart in wheat to capture all of the ryegrass seed,” he noted. “Then we have piles of chaff that are laced with weed seed that we can dump in a field and easily burn.”

Norsworthy tested his chaff cart during soybean harvest at the Northeast Research and Extension Center, located at Keiser in northeast Arkansas, last fall.

“We were quite successful in catching the soybean chaff, catching the pigweed seed and destroying those during the burning operation,” he said. “In addition to that, we’re also looking at narrow-windrow burning.”

To accomplish that, Norsworthy and his associates take the spreaders off the combine, form a narrow chute on the back of the combine and windrow the soybean chaff. “The soybean chaff, again, is laced with weed seed, and we burn that shortly after harvest.

“I have a graduate student who is conducting research on how effective we can be at destroying the weed seed in soybean chaff, which obviously is quite different than the system they’re using in Australia.”

Another tool Norsworthy and his researchers are looking at is the Harrington Seed Destructor, which is pulled behind the combine. (For more on this implement, see As chaff enters the Destructor, any weed seed contained is ground and destroyed before being passed back onto the field.

“Obviously, there isn’t any loss of the chaff or straw because it essentially is a grinding operation,” said Norsworthy.

Ray Harrington, the inventor of the Harrington Seed Destructor, and Lance Turner, an Australian grower who uses a chaff cart similar to Norsworthy’s will be at Keiser for a meeting on the afternoon of Aug. 18.

“We’ll also have a grower from Australia talk about the impact of narrow windrow burning those practices have had on resistance management in the Australian system and what some of our growers in the U.S. could do to try to manage herbicide-resistant weeds,” said Norsworthy.

“At the end of the day, the key to resistance management is bringing down the soil seed bank,” he said. “We’re doing a tremendous amount of chopping and hand removal at this point, and these are strategies we could possibly integrate into our production systems to reduce the amount of weed seed going back into the soil seed bank.”

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