Western Australia
October 2, 2017

Weeds have been particularly hard to manage in parts of the Western Australian grainbelt this year, given the late season break and earlier extended dry period that has affected many areas.


A plastic chute fitted to the harvester funnels the chaff containing the majority of weed seeds present into a narrow band in the middle of the CTF run. PHOTO: Mic Fels

Moisture stress had a major impact on the efficiency of weed kill through the growing season, making harvest weed seed control (HWSC) essential to reduce the weed seedbank, help conserve soil moisture during summer and slow the evolution of herbicide resistance.

Peter Newman, from the Australian Herbicide Resistance Initiative (AHRI) and the Grains Research and Development Corporation (GRDC)-supported industry WeedSmart project, says chaff lining is one of the easiest and most cost-effective HWSC tactics available.

“Chaff lining is a relatively new practice that makes a narrow windrow of chaff only down the middle of the harvester,” he said.

“Weed seeds are concentrated in that zone and straw is spread as usual.

“The chaff line is not burned, but left on the soil surface for weed seeds to rot. Any plants that do emerge have to compete with each other in a narrow row, leaving the remainder of the subsequent crop area clean.

“The harvester needs to follow the same tracks each year, to make sure the chaffline is dropped on the old one, but this can be done even without using a full Controlled Traffic Farming (CTF) system.”

Mr Newman said many WA growers were making their own chaff chutes and some were using a baffle to optimise the number of weed seeds diverted to the chaff line.

Other growers are burning the chaff line by placing a conventional narrow windrow over the chaff line every few years. This is typically being done in a canola phase, when a hot and effective burn can be achieved, to destroy even more weed seeds and remove the chaff that has built up.

He said other common HWSC methods being used in the State to reduce weed seedbanks included:

• Collecting chaff in chaff carts
• Using the Bale Direct system to collect straw and chaff as it exits the harvester
• Depositing chaff on narrow windrows for burning the next autumn
• Using seed destructor technology to pulverise chaff fraction as it leaves the harvester
• Diverting chaff onto permanent tramlines (in controlled traffic farming systems) or into narrow rows.

WeedSmart has a series of videos showing different methods of managing chaff during harvest, available on its website: https://weedsmart.org.au/setting-up-harvesters-to-capture-weed-seed-in-the-chaff/

There is also a case study featuring Esperance and Three Springs grain growers Mic and Marnie Fels, who have been using chaff lining for several years, at https://weedsmart.org.au/case-studies/fels-family-wa

An online course that explains HWSC tactics, including chaff lining, can be accessed at: http://www.diversityera.com/courses/harvest-weed-seed-control-101

For more information about Integrated Weed Management strategies, including options for harvest, go to the GRDC website at: https://grdc.com.au/resources-and-publications/iwmhub and Weedsmart: www.weedsmart.org.au

Website: http://www.grdc.com.au

Published: October 2, 2017