Weed seed control technology will be on full display at this year's Farm Progress Show Aug. 30-Sept. 1. Learn the latest strategies from Iowa State University Extension and Outreach. Harvest Weed Seed Control At harvest time, weeds that have escaped season long management often have mature seed still attached to the parent plants. These weed seeds can enter the combine along
Weed Seed Destructor and Other Control Methods to Be Showcased
AMES, Iowa – Controlling weeds in farm fields is an annual challenge – especially with more weeds becoming resistant to herbicides.
Fortunately, producers have a wide range of options to counter weeds, including some creative ways that may not have been employed in the past.
At this year’s Farm Progress Show, Aug. 30-Sept. 1 in Boone, Iowa State University Extension and Outreach will showcase one of the more innovative, and practical methods of controlling weeds: a weed seed destructor.
Fitted to a combine, the weed seed destructor does what it’s name implies. It pulverizes and destroys seeds so that they cannot germinate.
The weed seed destructor (by Redekop) will be attached to the back of a John Deere 680 combine and will be available for viewing outside the ISU Extension and Outreach tent. While the machine will not be operating during the show, visitors can see it in operation on a computer screen, and they can ask questions of weed science experts.
“We want to give the public a chance to see and ask about this innovative form of weed control technology,” said Prashant Jha, professor and extension weed specialist at Iowa State. “Farmers in central Iowa and in Harrison County are already using this technology and we expect more will do so in the coming years.”
Other methods of weed control will also be featured, including videos of chaff lining, a method that guides the harvested chaff into narrow bands as it flows out the back of the combine at harvest, which reduces the spread of weed seeds by more than 95% across the fields and contains weed seeds in smaller spaces.
The harvester or combine is modified with a baffle that separates the chaff (containing the majority of weed seeds) from the straw. The chaff is directed into narrow central bands using a chute at the rear of the combine.
Weed seeds in the chaff are subjected to decay, and burial of small-seeded weed species such as waterhemp in the chaff will potentially result in reduced emergence in the subsequent growing season. High application rates of herbicides or shielded sprayers can be used to selectively control emerged weeds in those narrow bands in the field.
The weed control display will also allow visitors the chance to test their knowledge of weed specimens found in the Midwest. Sixteen different species will be available for visitors to identify.
Visitors will also have the chance to learn more about waterhemp, and how it can be suppressed using cereal rye as a cover crop. Photos and sample trays will show the results of using no rye, rye terminated at 4-6 inches tall, and rye terminated close to heading.
“We’re going to be showing the potential for biomass (cover crops) to suppress weeds like waterhemp, and how the results vary based on the height of the cover crop,” said Jha.
Cereal rye has the best potential to suppress weeds because it accumulates more biomass than other cover crop species. A study that was done for the Farm Progress Show shows an incremental decrease in waterhemp based on the density of rye.
Field studies indicate cereal rye biomass of 4,500 to 5,000 pounds per acre at termination can significantly suppress waterhemp emergence in soybeans, and reduce the size and density of waterhemp at the time of exposure to postemergence herbicides.
Additionally, producers can view a map of where herbicide resistance has been documented in Iowa based on the recent survey, and ask questions to Jha and other specialists about their own experience with herbicide-resistant weeds.
Jha will be joined at the show by ISU Extension and Outreach field agronomists Angie Rieck-Hintz, Meaghan Anderson, Gentry Sorenson and Mike Witt and several weed science graduate students.
Harvest Weed Seed Control
At harvest time, weeds that have escaped season long management often have mature seed still attached to the parent plants. These weed seeds can enter the combine along with the cash crop, exit the back of the combine as chaff (small plant pieces and weed seeds), and be spread across the field, as well as from one field to another. It seems a waste to spend all year spraying weeds with expensive herbicides only to reward the survivors at harvest by spreading their weed seeds out for next year.
An excellent way to stop weeds in their tracks is to collect these weed seeds at harvest and either destroy them or deposit them in a known location where they can be monitored and controlled later. Soybean, wheat, and other crops harvested with a grain header are ideal choices for harvest weed seed control (HWSC). Other crops such as cotton and corn need further equipment development to make HWSC a viable option.
If you are considering adding harvest weed seed control (HWSC) to your weed control program there are excellent resources on the WeedSmart website to help guide you through the initial decisions and the implementation of this important weed control tool.
3 steps to get it working for you
1. Decide which system fits your farm best.
2. Get maximum weed seed into the header.
3. Know how to manage the collected weed seed.
What is Harvest Weed Seed Control?
Choose The Best System For You
Which system is best?
HWSC is being rapidly adopted in Australia and other countries around the world. There are six systems currently being used on Australian farms and they have been initially developed by farmers.
Research has demonstrated that all are very effective weed seedbank management tactics for a range of weed species, achieving over 80 percent control and for some nearly 100 percent.
See HWSC in Action
Over 80% weed control for species that retain seed at harvest
Crop residue management
There are six systems currently used to collect and manage weed seed at harvest. They can be grouped according to the way crop residue is managed: chaff only or chaff + straw.
Chaff carts are a tow-behind unit on the combine that collects the weed seed-laden chaff, which can then be placed into piles that are later either grazed by livestock, burnt, or both and sown through the following season. Chaff carts are often chosen for use on mixed cropping and livestock farms in Australia as the chaff is an excellent livestock feed; however, spreading manure back onto fields can allow for further seed spread.
Chaff lining funnels the chaff and weed seeds into narrow rows behind the combine, where the residue is left to overwinter. The weed seeds are exposed to natural elements that can lead to weed seed decay and predation. Typically a follow-up herbicide application is required. – Chaff lining is usually considered a good entry-level HWSC option.
Chaff decks (chaff tramlining) are similar to chaff lining, but place the chaff in one or both of the combine’s wheel tracks. The added compaction from the wheels can be beneficial in controlled traffic systems.
Impact mills run the chaff through a mill that pulverizes (destroys) the weed seed, which is then spread across the fields. This technology is usually considered the ultimate in HWSC.
CHAFF + STRAW
Bale direct collects all the crop residue directly from the combine and compacts it into large bales suitable for sale.
Narrow windrow burning collects all of the crop chaff and straw residue, and funnels it into narrow rows in the field. These rows are burnt to destroy the weed seed. This method is effective but removes all of the crop residue from the field.
Learn More About Each System in This Research Report
Calculate the cost
While each HWSC tactic is similarly effective in collecting weed seeds , they vary considerably in capital and ownership cost, nutrient removal costs, operational costs, and labor costs. Some HWSC tactics involve the purchase of substantial machinery – such as an impact mill, chaff cart, or chaff deck – but the operational and labor costs might be lower than methods such as narrow windrow burning, which involves low set-up costs but higher nutrient losses and labor costs associated with burning. Chaff lining is often chosen as the best entry-level tactic that requires minimal set-up cost, no additional labor and minimal nutrient loss or redistribution. To calculate the cost of each method for your farm you can use a calculator developed by WeedSmart’s Peter Newman. Download the calculator or learn more @ Calculating the cost of HWSC for your farm.