The Liberal Democrat MP for the Somerset constituency of Somerton and Frome is set to start first full week as a government minister.
He was appointed to the role by Prime Minister David Cameron in the government reshuffle last Tuesday (4 September).
Mr Heath replaces Jim Paice, Tory MP for south-east Cambridgeshire.
Writing on his website, Mr Heath said his constituency was one of the country's most important dairy farming areas.
"There is an enormous amount of work to do to ensure a fair deal for rural communities and a fair return for primary producers," he said.
"I am looking forward to working with the new [Defra secretary] Owen Paterson, who represents a very similar constituency in rural Shropshire, to make that a reality.
"At the same time we need to protect rural services, grow the economic opportunities in countryside areas, and balance the needs of often fragile environments."
Elected to parliament in 1997, Mr Heath previously served as leader of Somerset County Council and also acted as Parliamentary consultant for the World Wide Fund for Nature.
In Parliament, he has held a number of front-bench positions, including Lib Dem spokesperson for agriculture, and as a spokesperson for work and pensions.
Mr Heath has also served on the science and technology select committee. Until his appointment as a Defra minister, he served as deputy leader of the House of Commons.
A graduate of Oxford University where he gained an MA in Physiological Sciences, Mr Heath subsequently took further studies in Ophthalmic Optics at City University.
As Defra secretary, North Shropshire MP Owen Paterson will have overall responsibility for the department.
The Tory joins Defra after serving in the Cabinet as secretary of state for Northern Ireland from May 2010.
Like Mr Heath, Mr Paterson was elected to Parliament in 1997.
In opposition, he held positions as shadow agricultural whip, shadow farm minister, shadow transport minister and shadow Northern Ireland secretary.
Born in Whitchurch, Shropshire, Mr Paterson read history at Cambridge University and speaks French and German.
Before entering politics Mr Paterson joined his family's leather business, where he became managing director in 1994.
Outside of politics he is interested in horses, racing and eventing, architecture, trees and history.