Farmers and Australian landholders will stage "the world's longest protest" along 5800km of highways in opposition to coal and gas mining.

Protesters are set to line their trucks, utes and tractors across numerous states and territories from the east to west in defence of water and food-processing land.

The group plan to hold banners on Saturday that encourage motorists to vote for water and against gas, as part of the Water4Life campaign.

In NSW, the protest will span the Pacific, Newell, New England, Hume and Bruxner Highways, and Thunderbolts Way.