The news was announced in an announcement to the ASX last Friday, but there was no reason given for Mr Irwin's sudden departure.

However, the common whisper from Rural Press’s sources is that the decision for Mr Irwin’s departure boiled down to a personality clash between him and his management team, and him and the board.

Multiple sources confided off the record that there were issues with Mr Irwin’s management style, which put many within the company offside, however nobody had formally commented on these rumours.

Mr Irwin's two year stint at the helm of GrainCorp was a busy period for the company.

In that time, GrainCorp launched an unsuccesful bid for Ridley, before last year making the massive purchase of United Malt Holdings, making it one of the largest maltsters in the world.

GrainCorp chairman Don Taylor publicly applauded Mr Irwin's efforts, saying he had oversaw a transition period in the company.

In a prepared statement Mr Irwin said he parted with GrainCorp on good terms, but gave no indication of why he was leaving.

"I have enjoyed my time at GrainCorp and appreciate the support provided to me by both employees and the board for the significant process and cultural changes necessary to compete in the deregulated Australian wheat market," he said.

GrainCorp officials would not publicly comment on the reasons for Mr Irwin’s exodus, other than to say that it was nothing to do with the financial performance of the company.

Meanwhile, former GrainCorp chief financial officer Ian Wilton has been appointed as caretaker chief executive.

Prior to coming to GrainCorp in June of last year, Mr Wilton was CFO at ConAgra Malt, the company that evolved into UMH.

Mr Taylor said a new global search had been launched to find a replacement for Mr Irwin, and that a result was expected within three to six months.

GrainCorp’s share prices has fallen by 7.68pc since the news of Mr Irwin’s departure, from $6.25 to $5.77.