For 43 years, 37 in Oamaru, Mr Whitham has worked with crops.
He said he was looking forward to his retirement but would miss "the connection with the farmers".
Mr Whitham started his career as a ground seed agent in Culverden, in 1980, where he worked for six years.
He then moved to Oamaru and continued the work until he joined Stringer & Company, in 1991, as an arable representative.
Stringer & Company was dissolved, the company went through several takeovers and is now PGG Wrightsons.
Over his time in the industry Mr Whitham experienced several changes, including the transition from paper to online and the introduction of cellphones and computers.
There had also been improvements in machinery, techniques and irrigation.
During his 43 years, he had worked with multiple generations of the same families.
"I’m dealing with third-generation farmers now."
Mr Whitham said the best part of the work was the people, both clients and colleagues.
"This business is easy when you have good relationships with your farmer clients."
The worst part of the job was the extensive driving.
"I’ve never had any major accidents, which I’m quite proud of."
In his retirement, he planned to spend time with his grandchildren and travel with his wife.
He said he had earned his retirement.
Mr Whitham’s last day will be next Friday.
