Federal Agriculture Minister Barnaby Joyce, who famously threatened to have Johnny Depp's dogs killed, has been accused in South Australian Parliament of using a bulldozer to kill frogs.

State Agriculture Minister Leon Bignell used Question Time to take aim at the shift of the water portfolio to the Nationals.

"Barnaby's view on water is that he likes to put the big hat on, start the D9 [bulldozer] up and as long as there's no frogs or lizards in the way — and if there are, don't say anything about them — and dig big dams, preferably in the north of the country," Mr Bignell told Parliament.

At that point, Riverland MP Tim Whestone jumped to Mr Joyce's defence.

"The Minister for Agriculture doesn't own a bulldozer and doesn't get on bulldozers to push frogs out of the way," Mr Whetstone said.

But Mr Bignell said his point about frogs had legs.

"I have actually sat around the table with Barnaby a few times. I get on very well with him and I know what his views are on D9s and frogs. So I think it's great that we've got [Riverland Senator] Anne Ruston and Barnaby Joyce working together," he said.

Mr Bignell made the comments while congratulating Senator Ruston for becoming Assistant Minister for Agriculture and Water, saying she would be an advocate for South Australia.

Premier Jay Weatherill has expressed concern about the shift of the water portfolio to the Nationals, but is hopeful Senator Ruston will make sure South Australia's interests are heard in Canberra.

"I'm very concerned about this. Barnaby Joyce is a vocal supporter of upstream irrigator interests," Mr Weatherill said.

"I am concerned about his appointment there's no doubt about that.

"But I'm also very heartened that Senator Ruston as a South Australian is there and I hope she's vigilant in protecting our interests and I'm sure she will be."

Mr Joyce responded later by telling reporters: "I do have a big hat. I do like dams and I too have enjoyed working with Leon Bignell."