Harvest weed seed control techniques might sound old-fashioned, but some scientists think they could become an important part of the future of American agriculture.
These techniques, which involve preventing weeds by mulching, pulverizing or burning weed seeds during harvest, are currently being used along with other integrated weed management tactics, such as herbicides, in other countries.
Lauren Lazaro, a weed scientist with the LSU AgCenter, is studying two promising forms of harvest weed control techniques at the Dean Lee Research Station in Alexandria and the Central Research Station in Baton Rouge. She is working with other AgCenter weed scientists, including Daniel Stephenson, Josh Copes and Donnie Miller.
“The whole point is to reduce the soil seed bank,” Lazaro said. “We want to impact that directly, and the goal with this technology is to not let any seeds go back into the soil at harvest.”
The techniques Lazaro is researching — chaff lining and chaff tramlining — involve funneling weeds and other material off the back of the combine into narrow rows to kill weed seed that have escaped other management strategies during harvest.
In chaff lining, the chaff residue from the back of the combine is funneled into one row and left to “let Mother Nature take its course,” Lazaro said. The material with the weed seed inside will mulch over and create a barrier that many seeds will not be able to penetrate.
The other technique, chaff tramlining, could possibly be more effective, Lazaro said. In tramlining, the combine funnels the chaff residue into two narrow rows on dedicated wheel tracks during harvest so that in addition to mulching, the farm equipment will run over it and compact it.
Lazaro has tested a third technique, narrow windrow burning, which involves funneling chaff and straw residue containing weed seed into rows and burning them. However, AgCenter researchers have moved away from the burning method because the smoke from burning windrows could irritate neighbors and create a hazard on highways near fields.
These weed control methods have become common in Australia, where about 80 percent of farmers use one of six harvest seed control techniques in addition to other integrated weed management tactics. Using a diverse set of methods to control weeds can help preserve current control methods, including herbicides used against herbicide-resistant weeds, Lazaro said.
Also, harvest weed seed control techniques could eventually reduce farmers’ herbicide use if the soil seedbank is reduced enough. But Lazaro cautions that producers will probably see no reduction in the soil seedbank for about the first five years if only a harvest weed seed control tactic is added to current management practices.
“That’s where we are seeing weed management research headed — away from herbicide use,” Lazaro said. “We don’t have any new herbicides coming down the pipeline any time soon as far as we know. We have to be able to preserve the ones we are using while utilizing additional integrated weed management options.”
Some harvest seed control techniques are cost-prohibitive for many producers. An impact mill, such as the integrated Harrington Seed Destructor, is installed in a combine and can kill most of the weed seed gathered at harvest. These cost about $60,000, and a commercial combine requires two machines, Lazaro said.
But the chute required to funnel residue into windrows for chaff lining and chaff tramlining can be built for about $300 in materials, Lazaro said.
“It is cost-effective,” Lazaro said. “Harvest weed seed control does not have to be a major overhaul on your equipment. You can do it on your own. And if that is another effective way to help control weeds, then why not use it?”
One drawback of the chaff lining and chaff tramlining methods of weed control is that these practices confine harvest chaff residue to one or two lines in the field instead of spreading the straw and chaff material all over, Lazaro said. This removes a layer of material that protects the soil, so weed scientists studying harvest weed seed control are researching them in conjunction with cover crops.
For now, these techniques are just being studied at AgCenter research stations, but soon they could move to on-farm studies.
“We’re starting out with small-plot trials and, we hope, once we begin to understand the system better, we would like to move these onto grower fields. Large-scale trials and grower adoption is how we will begin to see larger effects and be able to work out any issues,” Lazaro said. “Then we can see if we are seeing a larger reduction in weeds over time than compared to the systems that are being implemented currently.”
While harvest weed seed control may appear primitive, Lazaro said it is working elsewhere. It could be a part of American farmers’ futures.
“Be open to this type of technology,” Lazaro said. “It might seem a little bit odd, but it is a viable option in your field. Give it a chance.” Kyle Peveto
The chaff tramlining and chaff lining methods involve funneling weeds and other material off the back of the combine into narrow rows to kill weed seed that have escaped other management strategies during harvest. The chute required to funnel residue into windrows for chaff lining and chaff tramlining can be built for about $300 in materials, according to researcher Lauren Lazaro. Photo provided by Lauren Lazaro