Stubble burn-offs may startle a visiting city-dweller with their plumes of smoke billowing through the twilight, but the fires can be environmentally friendly.
Stubble burn-off is carbon neutral because the farmer has first drawn the original CO₂ in from the atmosphere by growing the crop.
In fact, with roots being retained and having far greater mass than the stubble above ground, the cycle is carbon negative with carbon being stored underground which will aid the next crop.
Weeds that grow between a crop and then remain after harvest are more likely to be herbicide resistant as evidenced by them still flourishing; therefore, they need to be destroyed before they set seed.
A ‘clean slate’ for a paddock also allows for better weed control before another crop is sown, particularly with pre-emergent herbicides, and also avoids header tines getting clogged during the next harvest.
The black carbon particles in smoke absorb light and so heat up the air; the lighter coloured organic aerosols cool it.
Smoke may cause problems with asthmatics, but the particles of smoke fall to the ground eventually.
Stubble burn-offs usually occur in autumn, but some farmers make use of a cool break before the summer heat sets in.
The CFA has registration specifications in terms of number of people and water supply on hand when conducting stubble burns.