Section 6: Managing weeds at harvest
Harvest in action producing
narrow chaff rows for burning
the following autumn
Weed seed capture and control at harvest can assist other tactics to put the weed seed bank into decline. Up to 95% of annual ryegrass seeds that enter the harvester exit in the chaff fraction. If it can be captured, it can be destroyed or removed.
Western Australian farmers and researchers have developed several systems to effectively reduce the return of annual ryegrass and wild radish seed into the seed-bank, and help put weed populations into decline.
A key strategy for all harvest weed seed control operations is to maximise the percent of weed seeds that enter the header. This means harvesting as early as possible before weed seed is shed, and harvesting as low as is practical e.g. 'beer can height.'
IWM manual section on harvest weed management
6.2 Narrow windrow burning
During traditional whole paddock stubble burning, the very high temperatures needed for weed seed destruction are not sustained for long enough to kill most weed seeds. By concentrating harvest residues and weed seed into a narrow windrow, fuel load is increased and the period of high temperatures extends to several minutes, improving the kill of weed seeds.
IWM manual section on narrow windrow burning
Narrow windrow burning in southern NSW, Grass Roots Ag (2014/15)
The nuts and bolts of efficient and effective windrow burning (2015)
Windrow burning for weed control - WA fad or viable option for the east (2013)
IWM - Narrow Windrow Burning GRDC Youtube clips
Narrow windrow burning - windrow chute design
Andrew Messina, (WA grower) explains his experience with designing and using a windrow chute on the back of the header. Home made, simple design, how to connect and disconnect, tips on optimum design for efficient windrow burning.
Narrow windrow burning
Michael Walsh, (AHRI) explains the subtleties of burning narrow windrows in canola, pulse and cereal crops. How weather conditions, fire temperature and type of crop stubble all contribute to destruction of the weed seed.
Narrow windrow burning - Vary Windrow Placement to Avoid Potassium Concentration
Peter Newman from AHRI describes why growers need to vary windrow placement to avoid potassium concentration.
Windrow burning (WeedSmart YouTube clip 2013)
Burning windrows for weed control (DAFWA YouTube clip 2012)
Narrow windrow burn like a pro (WeedSmart Youtube video 2015)
NWB Show and Tell video 1: paddock experiences in SNSW (Grass Roots YouTube video 2015)
NWB Show and Tell video 2: chute designs from the growers' perspective (Grass Roots YouTube video 2015)
Over the Fence: Windrow burning beats wild radish (2011)
6.3 Chaff Carts
Chaff cart in action at
Tarin Rock, WA.
Photo: A. Storrie
Chaff carts are towed behind headers during harvest to collect the chaff fraction. Collected piles of chaff are then either burnt the following autumn or used as a source of stock feed.
IWM manual section on chaff carts
IWM - Chaff Carts GRDC YouTube clips
Chaff Carts - Weed Seed Bank Destruction - More Efficient Use of Chaff Carts
Peter Newman from AHRI, explains methods for effectively managing chaff heaps at and after harvest.
6.4 Bale direct systems
The bale direct system uses a baler attached to the harvester to collect all chaff and straw material. This system requires a large baler to be attached to the back of the harvester. As well as removing weed seeds, the baled material has an economic value as a livestock feed source. (See http://www.glenvar.com/ for the story and development of header-towed bailing systems).
IWM manual section on bale direct systems
6.5 Harrington Seed Destructor
The HSD is the invention of Ray Harrington, a progressive farmer from Darkan, WA. Developed as a trail behind unit, the HSD system comprises a chaff processing cage mill, chaff and straw delivery systems. The retention of all harvest residues in the field reduces the loss and/or banding of nutrients and maintains all organic matter to protect the soil from wind and water erosion, as well as reducing evaporation loss when compared with windrow burning, chaff carts and baling.
IWM manual section on Harrington seed destructor
IWM - Harrington Seed Destructor GRDC YouTube clips
Weed Seed Destruction - Beer Can Height - Ray Harrington, WA grower and inventor of the Harrington Seed Destructor discusses the importance of lowering the cutter bar on the header to capture as much weed seed as possible for effective harvest weed seed management.
Weed Seed Bank Destruction - Lessons Learned - Windrowing Canola - Ray Harrington, (WA grower and inventor of the Harrington Seed Destructor) experience with weed seed capture when windrowing canola. Different approaches for managing blowouts at harvest and in the following crops
Weed Seed Bank Destruction - Spear grass (Bromus spp.) an Emerging Problem - Ray Harrington, (WA grower and inventor of the Harrington Seed Destructor) success with capturing spear grass (Bromus species) in the header and destroying the seed in the Harrington Seed Destructor (HSD).
Harrington Seed Destructor (WeedSmart YouTube clip 2013)
Groundcover episode on Integrated Weed Control and Harrington Seed Destructor (2010)
Development of the Harrington Seed Destructor (2011)
6.6 Further information
Tactic Group 4, Part 4 of the Integrated Weed Management Manual- Weed control at harvest
GRDC fact sheets and other publications
The effectiveness of on-farm methods of weed seed collection at harvest time: Case studies of growers in the Albany Port Zone (2013)
Managing the weed seedbank (2010)
Barry Gray, WA - Case study on Harvest systems combined to crush weed-seed resistance (2014)
GRDC Webinar on beginners guide to harvest management (2014)
This webinar is designed to provide some helpful tips for advisers and growers who wish to explore this option however may be unsure where to start. Topics that will be explored include why to consider harvest weed seed control; what options are available; what paddocks to target; and how to achieve success. Presenters: Mike Walsh (AHRI) & Maurie Street (GOA)
IWM – Seedbank Capture at Harvest GRDC YouTube clips
Weed Seed Destruction - Weed Seed Management GRDC YouTube clip
Peter Newman from AHRI explains the importance of harvest weed seed capture and management for getting the weed seed bank into decline.
Weed Seed Destruction - Weed Seed Capture GRDC YouTube clip
Peter Newman from AHRI outlines the different weed seed capture systems and the issues to consider when deciding which best suits a farm business. Issues include: effectiveness of capturing weed seed, nutrient removal and capital cost.
Groundcover episode on Harvester Mounted Weed Destructor (2013)
Groundcover episode on Harvest Weed Seed Control (2014)
Setting up your header for harvest weed seed control (WeedSmart YouTube video 2015)
Control harvest weed seed set with windrows and crop topping (WeedSmart YouTube video 2015)
Sustaining herbicides with harvest weed seed management (AHRI YouTube clip 2012)