Grain growers in the southern cropping region are being encouraged to now start thinking about using narrow windrow burning as a weed seed control tool to be employed at harvest this year.
Growers should consider – well ahead of harvest – which paddocks and crops would be most suitable for narrow windrow burning.
Grain Orana Alliance chief executive Maurie Street says for narrow windrow burning to be successful, growers should plan for its use “a long time before they strike a match”.
Speaking at recent Grains Research and Development Corporation (GRDC) grains research Updates, Mr Street said narrow windrow burning had proven to be successful in reducing key weeds such as annual ryegrass and wild radish in Western Australia and there was no reason to doubt its effectiveness on those same weeds in farming systems in the southern cropping region.
He said herbicide resistance was rapidly becoming more widespread and growers needed to act to save those herbicides which remained effective.
“Harvest weed seed control is a suite of tools to combat this, and narrow windrow burning is the cheapest and easiest to implement,” said Mr Street, whose research is supported by the GRDC.
Narrow windrow burning involves placing crop residue in a narrow windrow during harvest and then burning it.
“Research has shown that a large percentage of weed seeds that enter a header at harvest, exit in the trash fraction with the chaff and to a lesser extent, in the straw fraction,” Mr Street said.
“If you can capture and concentrate on those seeds and render them sterile by burning them, they’re not going to be there to germinate and compete with next year’s crop, hence breaking the weed’s reproductive life cycle.”
Mr Street said WA growers, the majority of whom now used narrow windrow burning to some extent on their farms, had shown that it was possible to burn only windrows and not the whole paddock.
He said two simple factors made this possible – cutting the crop low and suitable weather conditions.
“The crop needs to be cut short to capture weed seeds into the header front. Then the entire trash from the header is deposited in a defined, narrow windrow and not spread back over the paddock,” Mr Street said.
“This means the fuel load is in the windrow and not outside of it and the fire can only burn where there is fuel,” Mr Street said.
“Obstructions or hindrances such as rocks, sticks, gilgais or poor header driving skills that stop you harvesting low can reduce the effectiveness of narrow windrow burning. Address these issues ahead of time if possible.”
Mr Street said weather conditions when windrow burning needed to be calmer and cooler than those required for more traditional paddock burns which relied on more heat and wind to ensure the fire carried.
“However, despite these points, the fire can still get away to burn the whole paddock. Bulky cereal crops with thick stubble will be most prone to the fire getting away,” he said.
“So it is recommended, especially if inexperienced, to target lighter-yielding cereal crops or break crops such as canola, chickpeas, lupins or field peas that tend to have lower levels of trash remaining outside the windrow.
“Barley stubbles in particular have a reputation for being more difficult to burn without fire escapes and may be better left for when you are more confident in narrow windrow burning.”
Mr Street advises growers considering narrow windrow burning for the first time to identify well ahead of harvest which paddocks in which they intend to windrow burn. The following key points in relation to weed types can assist with decision-making:
- Narrow windrow burning has shown to be very effective on weeds that retain their seed at harvest above 15 centimetres, such as ryegrass and wild radish, making it easy to capture these weed seeds in the header front.
- Wild oats, brome or barley grass that shed or drop their seed may do so before the header has a chance to capture those seeds so these may not be reliable candidates for windrow burning.
- Short weeds, such as wireweed, that set seed lower than practical to capture in the header front are not ideal candidates.
- Weeds that are able to re-sprout or re-seed after harvesting, such as fleabane and sow thistle, are also not likely to be good targets for windrow burning.
Growers seeking more information on narrow windrow burning and other IWM practices can view GRDC ‘how to’ YouTube videos.
Multimedia resources about sustainable IWM practices are also available at www.ahri.uwa.edu.au and www.weedsmart.org.au. More information on IWM can be found at the GRDC’s IWM Hub.
Read the GRDC southern region Paddock Practices advice column on narrow windrow burning.
To download and listen to a GRDC Driving Agronomy podcast interview with WA grower Doug Smith on his experiences with narrow windrow burning.
Maurie Street, Grain Orana Alliance
Sharon Watt, Porter Novelli
Caption: For narrow windrow burning to be successful, growers should plan for its use “a long time before they strike a match”. Photo: M Street