Tossing waste such as silage wrap, chemical containers and tyres into fires when burning off can produce toxic smoke, the Environment Protection Authority has warned.
Landholders have been encouraged with recycle where possible this burn-off season.
Silage wrap, some chemical containers and tyres can be made into building and fencing materials and floor matting.
EPA North West Regional Manager Dr Scott Pigdon said many waste items would produce toxic smoke.
"Farm waste items like silage wrap, chemical containers and old tyres don't burn properly, but it will produce toxic smoke, and can send residue into waterways and create chemical contamination that persists in the soil," he said.
"Send it to landfill or a recycling facility."
The EPA said that fallen trees or other natural wood being burnt should be as dry as possible to keep down the volume of smoke.
Farmers have also been advised that they should check they have relevant council or Country Fire Authority permits.
The EPA said that timber from buildings, furniture or other manufactured products must not be burnt because of possible chemical treatments.
Offenders can be fined more than $8,000 by the EPA for burning anything other than vegetation-sourced matter like timber and crop stubble.
"Most farmers understand the importance to their livelihood and their community of preventing contamination of the soil, water and air around them, and EPA uses a fine as a last resort," Dr Pigdon said.
"By thinking twice about what goes onto the pile when burning off, you can protect the environment and the wellbeing of your farm, your family and your neighbours."
EPA urges people to report suspected pollution to the EPA on 1300 372 842 (1300 EPA VIC). Information on waste disposal and recycling can be found at sustainability.vic.gov.au or on your local council website.