Extra weed management options during harvest

The toolbox approach is a well-used analogy for how to control weeds on farm i.e. a variety of methods should be utilised to reduce the weed seed bank and minimise the development of chemical resistance. In this article our cropping advisor Tim Bartimote looks at mechanical add-ons to your header at harvest, such as chaff decks and chaff lining, as cheap and effective additions to your toolbox.

Harvest is an important time for weed control. Weeds which have “escaped” chemical applications throughout the season are producing seeds. Reducing the spread of these seeds will potentially reduce the weed burden for following seasons. Weed seeds are often picked up by headers during harvest, depending on the weed seed size and the crop being harvested. A lot of these weed seeds end up being blown out the back of the header and redistributed across the paddock with the chaff.

Harvest Weed Seed Control (HWSC) includes several strategies which can include windrow burning, chaff carts, seed destruction, chaff lining and chaff decking among others. In this article we will focus on chaff lining and chaff decks. These options aim to capture weed seeds in the chaff as they pass through the header by separating it from the straw. Chaff is then compiled either on the wheel tracks, in the case of chaff decks, or in a singular row behind the header, in the case of chaff lining. Chaff is placed in the same spot each harvest forcing weeds to migrate over multiple seasons. These weeds are effectively placed in “jail”, strips of weeds begin to appear across the paddock where producers can use heavy-handed tactics such as shielded sprayers, higher chemical rates or stock to obliterate weed numbers. When placed on controlled traffic tracks, weeds also encounter a hostile environment, where they compete less with the crop. It should be noted that escapes from these tracks will need to be monitored.

The process to modify a header for chaff lining or decking is relatively straightforward but can be slightly different depending on the colour and model of the header. A baffle is placed to catch chaff as the fan blows it out the back. This baffle is angled to force chaff to fall straight down while the straw can pass over the top. Central West Local Land Services has created a small network of producers who have modified their own headers and are happy to talk to other producers. This network includes a variety of header models. If you're interested, get in touch with me with your header model details and I can connect you with someone who has the same or similar model.

Chaff decks or chaff liners come in a variety of shapes and sizes. As a result, cost can vary depending if the setup is homemade or bought as part of a kit. Prices range from $1,000 to over $20,000. For more information regarding header modifications to capture weed seeds in chaff, contact your Local Land Services ag advisor.

Further Reading:
Ruttledge A, McIntosh P, Broster J, Rayner A, Bell K, Walsh M, Widderick M (2018) Chaff lining and chaff tramlining to reduce problem weed populations, GRDC Update Papers. Available at: https://grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2018/12/chaff-lining-and-chaff-tramlining-to-reduce-problem-weed-populations