Mr. Bush said, "I know firsthand his deep commitment to a strong farm economy."
"He's a strong proponent of alternative energy sources such as ethanol and bio-diesel."
Johanns, born in Iowa and raised on a dairy farm, earned his law degree from Creighton University in Omaha, Neb. After clerking for the Nebraska Supreme Court, he practiced law with a private firm, according to Reuters.
He was elected governor in 1998 and in 2002 became the first Republican to win re-election in more than four decades.
Analysts said the nomination of Johanns, who still requires Senate confirmation, reflects the administration's move to focus on farm trade over the next four years.
As governor, Johanns led a delegation of Nebraska's farm and business leaders on a trade mission to Japan, Taiwan, China, Singapore and a handful of other nations.
He has also been an outspoken supporter of ethanol and sought to promote value-added agriculture, the term for changing the form of a product, such as milling wheat into flour, or producing something that has been demonstrated to add value, such as organic produce.
Seven of President Bush's Cabinet members have said they will not be part of his second term. Administration officials have said Health and Human Services Secretary Tommy Thompson may be next to announce his departure, the Associated Press reported.