Timing and temperature key to windrow burning weeds
A hot, slow burn is the key to effective windrow burning for northern region grain growers, who are increasingly adopting the practice to control herbicide-resistant weeds.
Grain Orana Alliance (GOA) chief executive Maurie Street says each weed variety has a critical temperature to burn at, for the seed to be destroyed – for example, ryegrass seeds must burn at 400oC for at least 10 seconds to be effectively destroyed.
Mr Street said the right preparation through harvest and choosing the right time and conditions to burn were the keys to ensuring a successful burn.
“Harvest height is critical; you need to cut short enough that you reduce your fire risk by ensuring you are not left with too much stubble and that the fuel is in the windrow,” Mr Street said.
“You also have to make sure that you are collecting the seed at the front of the header, otherwise it is not going to work.”
GOA is a grower solution group funded by the Grains Research and Development Corporation (GRDC), which is supporting the adoption of non-chemical methods of weed control.
Narrow windrow burning is conducted by farmers in autumn before seeding and involves burning 500mm to 600mm wide windrows of straw and chaff, in order to kill weed seeds. A successful windrow burn can destroy 99 per cent of annual ryegrass seeds in the windrow if executed well.
Mr Street recommended farmers burn late in the afternoon on a “typical autumn day” when extreme summer temperatures have started to drop off and in conditions that are not too windy, to reduce the chances of the fire getting away too quickly.
“Burning when the weather is too hot increases the chance of fire escapes, but burning when it is too cold can mean the critical temperatures for seed kill is not achieved,” Mr Street said.
“It is definitely a balance and getting it right will come with experience.”
GRDC ‘how to’ YouTube videos about windrow burning and other integrated weed management (IWM) practices are available at www.grdc.com.au/IWM-videos.
Photo caption: A hot, slow burn is required for windrow burning to effectively destroy weed seeds.