Outgoing Ravensdown chief executive Greg Campbell is worried that state-imposed regulations will limit on farm innovation.
Diack joins Ravensdown from his position as chief executive and executive director of Tait Communications in July.
He has over 30 years' experience of improving corporate performance, effective governance and driving growth.
Ravensdown chair John Henderson said Diack's experience across many industries, his rural connections and his grounded-yet-innovative approach, made him a compelling proposition for the board.
"The board is excited that its search for someone that offers strategic continuity and deliberate evolution has been successful.
"There's no doubt that our purpose of enabling smarter farming for a better New Zealand has never been more important and Garry is passionate about that direction."
A firm believer in the power of co-operative business models, Christchurch-based Diack is looking forward to helping take Ravensdown forward in a changing landscape.
"Large parts of my career have been devoted to helping harness the power of New Zealand agriculture to punch above its weight in domestic and international markets.
"I have been fortunate to have had the opportunity of advising the likes of CRT, Silver Fern Farms and the predecessors to Fonterra. Through these experiences and a directorship of the Ashburton Trading Society, I have witnessed Ravensdown forge true value-based relationships with its farmers and I am privileged to be given the opportunity to play my part in the challenges of tomorrow's farming," said Diack.
"I know that Ravensdown has invested in tools and technology that have potential to be win-wins for the environment and farm profitability," he says.