Donald Trump has nominated longtime ally Brooke Rollins for secretary of agriculture, completing his cabinet roster.

He made the announcement Saturday late afternoon, tapping the head of Maga-backed think tank the America First Policy Institute for the job.

"As our next Secretary of Agriculture, Brooke will spearhead the effort to protect American Farmers, who are truly the backbone of our Country," Trump said in a statement.

Her nomination marks the end of a whirlwind - and sometimes dramatic - spree of nominations to lead executive agencies.

Rollins has been a top Trump ally for many years, as the co-founder and president of the America First Policy Institute, a pro-Trump right-wing think tank.

A former White House aide during the president-elect's first administration, she served as director of the Office of American Innovation and acting director of the Domestic Policy Council.

Having grown up on a farm, Rollins was involved early with Future Farmers of America in addition to 4H, a nationwide agricultural club.

She graduated from the Texas A&M University with a Bachelor of Science degree in agriculture development and later worked as a lawyer.

If confirmed by the Senate, she would oversee farm subsidies, federal nutrition programmes, meat inspections and other facets of the country's farm, food and forestry industries.

She would also play a key role in renegotiating the trade agreement between the US, Canada and Mexico, which could involve imposing Trump's promised tariffs.

Rollins' nomination marks the end of Trump's picks for his cabinet - a group of 15 advisers who each helm a bureaucratic department within the American government.

Each nominee will have to be confirmed by the Senate.

Trump has chosen an eclectic array of cabinet picks, from Maga loyalists to former political rivals.

Some of his nominations - such as Robert Kennedy Jr for the Department of Health and Human Services and Matt Gaetz for attorney general - have raised eyebrows.

Kennedy, a former environmental lawyer and vaccine sceptic who ran against Trump as an independent before dropping out and endorsing him, would be in charge of the Food and Drug Administration.

Gaetz, a bombastic former Florida congressman who spearheaded the ouster of former House Speaker Kevin McCarthy, withdrew his nomination and resigned over allegations of sexual misconduct with a minor, soliciting for sex and illicit drug use.

Media reported that senators made it clear it would be difficult to confirm Gaetz for the job. Gaetz has denied wrongdoing, but said he withdrew from consideration because he was becoming a "distraction".

Trump did not waste time, quickly nominating Pam Bondi, a former Florida attorney general, to the post instead.

Another pick, Pete Hegseth, has also been embroiled in scandal, after a police report revealed new details about an alleged sexual assault encounter the former Fox-news host had with a woman in 2017.

Hegseth has denied any wrongdoing and claims the encounter was consensual. He was never arrested or charged.

Education secretary nominee Linda McMahon - the former CEO of World Wrestling Entertainment - has also been criticised for her lack of experience in education.