Arsonists are thought to be behind a 300-bale hay fire that forced a road to close.
The blaze started at Temple Bruer, near Sleaford, yesterday evening and raged until the early hours of this morning.
Sparks and smoke led to the A15 being closed until 7.20am and a nearby side road being closed until 9am.
The fire also spread to a nearby tree, which was felled due to its dangerous condition.
Lincolnshire Fire and Rescue believe the cause was deliberate.
Police are appealing for witnesses who may have seen anything suspicious at the scene.
Anyone with information should call 101 and quote incident number 531 of September 26.
Alternatively, they can call Crimestoppers anonymously on 0800 555111.