Many southern New South Wales growers will be turning their minds to windrow burning soon, and while there are a number of different methods, weed management specialist Andrew Storrie says there are definitely some do’s and don’ts.
The Agronomo agronomist said although growers can’t do anything about chaff windrows that have already been produced, it’s likely that windrows from a well set up header will have withstood considerable amounts of rain over summer and still be ready to burn.
“This is true even in cases of over 100mm of rain between harvest and burning, particularly in windrows which aren’t over threshed, therefore remaining open and aerated,” Mr Storrie said.
“Of course, the other critical factor in windrow burning as a method of harvest weed seed management is the meteorological conditions at the time when you start burning.
“The easiest way to gather these conditions is by using a good app which will tell you the Fire Danger Index (FDI), which is determined by temperature, humidity, wind speed and dryness of the fuel.”
Growers will need to measure these and add the figures into the fire index app to calculate the FDI, therefore requiring a weather meter, either hand-held or cab mounted as well as the app installed on their mobile phone.
Mr Storrie suggests Fire Tools by Mountain Pine Studio as a useful tool for both Android and Apple users and also suggests using the Bureau of Meteorology’s MetEye site for monitoring local predicted changes to wind speed and direction so growers can decide whether to press on or call it a night.
“The best place to start a burn is at between FDI 8 – 10. FDI 15 or higher is too high and less than FDI 5 is often too cool or damp,” he said.
“Starting when the index is too high means the fire will rarely stay in the windrow and the fire will burn out significant portions of the paddock.
“Too low and the windrows won’t burn as hot as is needed to kill the weed seeds in the row.”
Grains Research and Development Corporation (GRDC) research shows that to guarantee the destruction of the weed seeds growers need temperatures greater than 400 degrees for 10 seconds for ryegrass, and 500 degrees for 10 seconds for wild radish.
“Narrow windrow burning reduces the seedbank – which is one of the key components of integrated weed management in tackling the increasing problem of herbicide resistance,” Mr Storrie said.
“Given weather conditions are most important for this practice growers will be balancing the need for an intense burn to destroy the seeds with the risk of losing control of the fire.
“I strongly encourage growers to utilise these apps which are available to take some of the difficulty of that balancing act out of the equation.”