Harvest Weed Seed Control

The opportunity to target weed seeds during grain harvest was established many decades ago following the introduction of mechanical harvesting and the recognition of high weed-seed retention levels at crop maturity; however, this opportunity remained largely neglected until more recently. The introd … The Arkansas Agricultural Experiment Station is taking part in research to fight the battle against herbicide-resistant weeds. Harvest weed seed control – beyond windrow burning Herbicide resistance remains an ongoing challenge for Australian grain growers but the industry is continually innovating to minimise the risks.

Opportunities and challenges for harvest weed seed control in global cropping systems

The opportunity to target weed seeds during grain harvest was established many decades ago following the introduction of mechanical harvesting and the recognition of high weed-seed retention levels at crop maturity; however, this opportunity remained largely neglected until more recently. The introduction and adoption of harvest weed seed control (HWSC) systems in Australia has been in response to widespread occurrence of herbicide-resistant weed populations. With diminishing herbicide resources and the need to maintain highly productive reduced tillage and stubble-retention practices, growers began to develop systems that targeted weed seeds during crop harvest. Research and development efforts over the past two decades have established the efficacy of HWSC systems in Australian cropping systems, where widespread adoption is now occurring. With similarly dramatic herbicide resistance issues now present across many of the world’s cropping regions, it is timely for HWSC systems to be considered for inclusion in weed-management programs in these areas. This review describes HWSC systems and establishing the potential for this approach to weed control in several cropping regions. As observed in Australia, the inclusion of HWSC systems can reduce weed populations substantially reducing the potential for weed adaptation and resistance evolution. © 2017 Society of Chemical Industry.

Keywords: HWSC; Harrington Seed Destructor; bale direct system; chaff cart; chaff lining; chaff tramlining; herbicide resistance; iHSD; narrow-windrow burning; weed-seed retention.

© 2017 Society of Chemical Industry.

Similar articles

Shergill LS, Schwartz-Lazaro LM, Leon R, Ackroyd VJ, Flessner ML, Bagavathiannan M, Everman W, Norsworthy JK, VanGessel MJ, Mirsky SB. Shergill LS, et al. Pest Manag Sci. 2020 Dec;76(12):3887-3895. doi: 10.1002/ps.5986. Epub 2020 Aug 11. Pest Manag Sci. 2020. PMID: 32633078

Walsh MJ, Powles SB. Walsh MJ, et al. Pest Manag Sci. 2014 Sep;70(9):1324-8. doi: 10.1002/ps.3704. Epub 2014 Jan 20. Pest Manag Sci. 2014. PMID: 24318955 Review.

Gibson DJ, Young BG, Owen MD, Gage KL, Matthews JL, Jordan DL, Shaw DR, Weller SC, Wilson RG. Gibson DJ, et al. Pest Manag Sci. 2016 Apr;72(4):692-700. doi: 10.1002/ps.4039. Epub 2015 Jun 15. Pest Manag Sci. 2016. PMID: 25974869

Green JM. Green JM. Pest Manag Sci. 2014 Sep;70(9):1351-7. doi: 10.1002/ps.3727. Epub 2014 Feb 24. Pest Manag Sci. 2014. PMID: 24446395 Review.

Shahzad M, Jabran K, Hussain M, Raza MAS, Wijaya L, El-Sheikh MA, Alyemeni MN. Shahzad M, et al. PLoS One. 2021 Feb 18;16(2):e0247137. doi: 10.1371/journal.pone.0247137. eCollection 2021. PLoS One. 2021. PMID: 33600412 Free PMC article.

Cited by

Maity A, Lamichaney A, Joshi DC, Bajwa A, Subramanian N, Walsh M, Bagavathiannan M. Maity A, et al. Front Plant Sci. 2021 Jun 16;12:657773. doi: 10.3389/fpls.2021.657773. eCollection 2021. Front Plant Sci. 2021. PMID: 34220883 Free PMC article. Review.

Liu C, Jackson LV, Hutchings SJ, Tuesca D, Moreno R, Mcindoe E, Kaundun SS. Liu C, et al. Sci Rep. 2020 Nov 26;10(1):20741. doi: 10.1038/s41598-020-77649-z. Sci Rep. 2020. PMID: 33244093 Free PMC article.

Javaid Akhter M, Melander B, Mathiassen SK, Labouriau R, Vendelbo Nielsen S, Kudsk P. Javaid Akhter M, et al. Plants (Basel). 2020 Nov 5;9(11):1495. doi: 10.3390/plants9111495. Plants (Basel). 2020. PMID: 33167487 Free PMC article.

See also  Weed Seed For Hair Growth

Maqbool MM, Naz S, Ahmad T, Nisar MS, Mehmood H, Alwahibi MS, Alkahtani J. Maqbool MM, et al. PLoS One. 2020 Oct 28;15(10):e0240944. doi: 10.1371/journal.pone.0240944. eCollection 2020. PLoS One. 2020. PMID: 33112902 Free PMC article.

Kaundun SS. Kaundun SS. Pest Manag Sci. 2021 Apr;77(4):1564-1571. doi: 10.1002/ps.6072. Epub 2020 Sep 21. Pest Manag Sci. 2021. PMID: 32893405 Free PMC article.

Chaff Lining, Seed Mills Aid in Fight Against Herbicide-Resistant Weeds

WEED SEED CONTROL — Jason Norsworthy, left, Distinguished Professor of weed science with the Arkansas Agricultural Experiment Station, left, and Tom Barber, Professor and Extension weed scientist, are seen in 2018 with an Integrated Harrington Seed Destructor, part of the University of Arkansas System Division of Agriculture’s experiments with harvest weed seed control.

Media Contact

John Lovett

U of A System Division of Agriculture
Arkansas Agricultural Experiment Station
(479) 763-5929 | [email protected]

FAYETTEVILLE, Ark. — The Arkansas Agricultural Experiment Station is taking part in research to fight the battle against herbicide-resistant weeds.

Catching weed seeds before they start a new generation of herbicide-resistant plants is the tactic behind a relatively new method in the United States that weed scientists in Arkansas, Iowa, Kansas and Missouri have partnered to investigate.

“When you take a look at weed management in general, it’s all really centered around soil seed bank management,” said Jason Norsworthy, Distinguished Professor of weed science with the experiment station, the research arm of the University of Arkansas System Division of Agriculture. “If we can drive those soil seedbanks down it’s going to benefit us in terms of the future populations or densities we have in those fields as well as lessening the risk of herbicide resistance evolution and spread.”

The seeds can be caught in the chaff and crushed by a seed mill or laid down in a “chaff line” to consolidate and create a mulching effect, Norsworthy explained.

Since most of the weed seeds are in the chaff, chaff lining calls for a baffle and chute on the harvester that consolidates the chaff in a narrow row 20 to 24 inches wide on the ground behind the harvester. The chutes can be fabricated by farmers of bought commercially.

Seed crushers do as the name implies, catching the seeds and crushing them. But some seed crushers may work better for different kinds of crops and weed species. That is also part of the experiment station study.

Harvest weed seed control was pioneered in Australia by Michael Walsh, associate professor and director of weed research at the University of Sydney. The method has been widely adopted there to capture weed seeds as they come through a combine during harvest, Norsworthy said. Experiments in Arkansas on chaff lining and seed crushing have been conducted at the Division of Agriculture’s Northeast Research and Extension Center in Keiser.

Prashant Jha, professor of weed science at Iowa State University, showed that more than 95 percent of the weed seeds can be concentrated in a chaff line at the time of soybean harvest during a 2021 study in Iowa funded by the Iowa Soybean Association. Jha, who was a graduate student under Norsworthy at Clemson University, said his studies have shown that chaff lining reduces the spread of herbicide-resistant weed seeds.

The weed seeds that were concentrated into rows emerged four to six weeks later than usual, which allowed the herbicides to be more effective because the weeds were smaller, Jha said. By the time the weeds in the chaff line grew to 2-3 inches, the smaller number of weeds outside the rows had grown to 6-8 inches.

See also  Og Weed Seeds

Also taking part in the study is Vipan Kumar, assistant professor of weed science at Kansas State University. Kumar, who was a graduate student under Jha at Montana State University, said his wheat and sorghum chaff lining research in Kansas has shown to significantly reduce kochia and downy brome emergence.

“The mulching effect of chaff lining on weed seed banks further depends on the type of crop being used and the target weed species,” Kumar noted.

Cover crops, various herbicides and seed harvest tactics are part of the multi-level, multi-state experiment on harvest weed seed control, Norsworthy said.

In Arkansas studies on weed seed control, Norsworthy has also experimented with narrow windrow burning. This method collects the seeds in the chaff on the ground, but it is then burned. Norsworthy said his studies showed a 100 percent kill rate of weed seeds using windrow burning, and he has seen some row crop farmers in Arkansas effectively use this method. But he is researching other methods since burning creates issues that include smoke and carbon dioxide release.

After testing narrow windrow burning, Norsworthy tested the Integrated Harrington Seed Destructor. He said it was 99 percent effective in terminating pigweed seeds when the seed mill did not “clog up” in fields with green pigweed plants. Norsworthy is now testing a Redekop Seed Destructor, which he says does not have as much of a tendency to clog on green Palmer amaranth pigweed plants. A desiccate can be used to help dry the Palmer amaranth since the female plants remain green until a winter freeze, he said.

“The end goal is to protect yield potential in fields and reduce the risk of herbicide resistance,” Norsworthy said.

Harvest weed seed control – beyond windrow burning

Herbicide resistance remains an ongoing challenge for Australian grain growers but the industry is continually innovating to minimise the risks. Non-chemical tools are becoming mainstream practice so that growers and advisers can deal with herbicide resistance by reducing weed seed banks and protecting chemistry.

One of the most popular weed management tactics being adopted in recent years is harvest weed seed control (HWSC). This process takes advantage of seed retention at maturity by collecting weed seeds as they pass through the harvester. Problematic weeds such as annual ryegrass, brome grass and wild radish retain 77-95% of their seed above a harvest cut height of 15cm at maturity, creating an ideal opportunity for seed collection.

Seed retention will change over time with the proportion of retained weed seeds declining the longer harvest is delayed past crop maturity. Therefore, crop and weed maturity will have a significant impact on the success of harvest weed seed control. Harvest height is equally important for harvest weed seed control, with a 15cm cut height preferred to capture 80-90% of the ryegrass seed at maturity – this can be challenging in high yielding cereals or bulky hybrid canola crops.

In the southern cropping region, low harvest height has been a barrier to adoption with growers not wanting to slow harvest down, incurring higher fuel costs and reducing harvester efficiency. Growers and researchers have since been looking at tactics that will enhance the efficacy of harvest weed seed control without slowing harvest. One option being adopted is sowing crops at narrower row spacings or higher plant populations. Weeds are then forced to grow taller to compete for light, therefore producing seed higher in the crop canopy. Stripper fronts are also being investigated to gauge any differences with weed seed capture and harvest efficiency, reducing the need to cut low whilst minimising fuel consumption.

See also  Mac 1 Weed Strain Seeds

Harvest weed seed control (HWSC) practices

Originally pioneered 30 years ago with chaff carts in Western Australia, harvest weed seed control has now been adopted nationally as growers tailor their options to suit different farming systems and locations. The harvest weed seed control options are all slightly different with narrow windrow burning (NWB) and bale direct taking in both straw and chaff for burning or baling. Newer harvest weed seed control practices only take in the chaff fraction containing weed seeds for rotting, grazing or destruction through a mill. This includes chaff lining or chaff decks, chaff carts and emerging mill technology using the Integrated Harrington Seed Destructor (iHSD) or Seed Terminator.

Research by Walsh et. al., 2014 highlighted that harvest weed seed control tactics are equally effective in reducing weed seed production. The use of chaff carts, narrow windrow burning or the Integrated Harrington Seed Destructor, were compared at 24 sites across Australia with an average reduction in ryegrass of 60% germination the following autumn. This was achieved by removing 70-80% of the seed at harvest through either burning or destruction of weed seeds.

Research has recently commenced to gauge the impacts of chaff lining and chaff decks on the rotting of weed seeds under different crop types. Preliminary data suggests poor seed survival under canola or barley chaff because of an allelopathic effect; however in wheat there was high ryegrass seed survival underneath the chaff row which is unexplained. Michael Walsh from Sydney University and John Broster from Charles Sturt University are currently working to quantify the value of rotting under chaff line and chaff deck systems.

Each harvest weed seed control practice has its own benefits and challenges with growers leading the charge, working with a small group of researchers to develop harvester modifications that maximise weed seed control with harvest height and seed retention. For harvest weed seed control to be successful at the farm level the practice needs to be both cost effective and practical to fit in with existing operations.

Harvest weed seed control cannot be used in isolation for weed management; growers and advisers should implement a range of diverse weed management practices to drive weed numbers down. Defined as the ‘Big six’ (www.weedsmart.org.au/the-big-six), these management practices include diverse rotations, mix and rotating herbicides, crop competition, double knocks, crop topping/hay to stop seed set and harvest weed seed control. The ‘big six’ complements best practice agronomy such as calendar sowing combined with effective pre-emergent herbicide packages.

Harvest weed seed control adoption

An online twitter survey was conducted in November 2017 by WeedSmart with 269 growers responding. The results indicated that harvest weed seed control practices are changing, with narrow windrow burning declining at the expense of chaff lining and chaff decks. 32% of growers were planning to use narrow windrow burning in 2017 whilst 26% would be chaff lining and 9% using chaff decks. Chaff carts were stable at 13%, mill technology at 3% and 14% would be doing nothing.

The overall trend is positive and reflects the high value growers are increasingly putting on harvest weed seed control as a mainstream weed management tool, it does not come easy and looking at each practice in detail (Table 1) highlights what growers and advisers need to be aware of.