Southern NSW farmer Gerry Lane, from Milbrulong, became deputy chairman at a meeting on Thursday.

Mr Eastburn subsequently resigned from his group director's position at GrainCorp the following day, but Mr Mangelsdorf remains on the GrainCorp board.

Mr Eastburn's departure follows a sudden exodus of other GGA board members from GrainCorp, including Mr Lane, Spencer Millear and Bruce Smith, who resigned last month but remain on the GGA board.

Mr Eastburn's resignation means GrainCorp is operating with the minimum five board members and a managing director.

GrainCorp chairman Don Taylor confirmed Mr Mangelsdorf was still on GrainCorp's board as of Friday but could not elaborate on the West Wyalong grower's future with the organisation.

"That's up to Dan to decide," Mr Taylor said.

The chief executive officer of the association, Peter Flottmann, refused to comment, saying the GGA would put out a media release soon about the board restructure.

Meanwhile, GrainCorp has officially lodged the bidder's statement for its off–market takeover offer for all the issued shares in Ridley Corporation Limited with the Australian Securities and Investment Commission.

GrainCorp's offer for the stock feed manufacturer is aimed at making the grain company Australasia's leading handler and supplier of agriproducts and bulk products.

The offer is one fully paid GrainCorp share for every nine Ridley shares.