Before serving as agriculture secretary, Butz was on the faculty of Purdue University, eventually heading the school's department of agricultural economics in his home state of Indiana, The Indianapolis Star reported.
"Not many farmers can name the current secretary of agriculture, but back then every farmer knew Earl's name," Randy Woodson, dean of Purdue's School of Agriculture, said. "He will be remembered as helping farmers compete on a global stage and as a great leader for agriculture."
In 1976 he resigned from the Nixon administration, after a racial joke he made in a private conversation was made public.
"He certainly was one of the most politically incorrect politicians any of us have ever known," John Hardin, a Purdue trustee, was quoted by the newspaper as saying.
After resigning as agriculture secretary, Butz remained at Purdue as a volunteer professor. He also was on the boards of several agricultural companies and worked as a public speaker.
In 1981, he pleaded guilty to income tax evasion for underreporting lecture fees. He served a 30-day sentence.