Fire and Emergency New Zealand investigator Jason Hobbs said the fire was caused by fertiliser stored in the shed.
He said it was contaminated and had "self-ignited".
"It is a timely reminder for people to be aware of how they store their fertiliser," he said.
Two fire crews were called to the club on Mcleans Island Rd at 8.10am.
The shed, which had three tractors a front loader and truck, was destroyed in the fire.
