A Fire and Emergency New Zealand spokesman said the fire was reported on a property near Ida Valley-Omakau Rd about 6.30pm.
He could not say how many bales had been burnt, but about 200 were sitting together.
No cause had been determined.
A fire appliance from Omakau, two tankers from Naseby and Ranfurly and two rural response vehicles from Blackstone responded.
Two diggers were also on the scene to separate the bales or bury them if necessary. — APL