Rob Hewett will take over as chairman of Farmlands following the co-operative's annual meeting in November.
Incumbent chairman Lachie Johnstone confirmed last week he was not seeking re-election in this year's directors election.
Johnstone, of Waikato, joined the board of North Island-based Farmlands Trading Society Ltd in November 2000 and was at the helm when it merged with South Island-based CRT Co-operative in 2013.
The merger was one of the largest transactions in New Zealand that year.
He became the inaugural chairman of the newly created Farmlands Co-operative, which last year announced revenue of $2.39 billion and a profit of $12.2 million.
In a statement, Johnstone said his nearly two decades in governance with the rural supplies and services co-operative could be seen both as a positive and a negative.
Listen to Jamie Mackay's interview with Rob Hewett on The Country below:
It had been a privilege to have watched Farmlands grow its footprint nationally. At the same time, he had been vocal about the need for a stronger pool of candidates in rural governance.
"My view is 18 years-plus is plenty for one person with one organisation and I look forward to continuing to work with Farmlands as a shareholder, rather than a director," he said.
He would remain chairman of Wellington-based Centreport Ltd, alongside other portfolios.
Hewett, who farms in the Manuka Gorge, stepped down as chairman of Silver Fern Farms Co-operative earlier this year.
He remains a director of Silver Fern Farms Co-operative and is co-chairman of Silver Fern Farms Ltd.
He paid to tribute to Johnstone's legacy within Farmlands.
"Steering two significant businesses through a merger of this scale in New Zealand is no mean feat and Lachie has been a strong and steady presence at the board table."