The head of an agricultural training centre says wages on dairy farms are too low to attract young New Zealanders.
About 10 percent of dairy workers, mainly in the South Island, are now immigrants on temporary visas.
The dairy industry says it is struggling to attract young Kiwis to the work.
The director of the Telford farm training division of Lincoln University, Charles Lamb, said the problem came down to simple economics.
"Honestly, if I look at my kids, why, they wouldn't do it because they don't pay enough. If they wanted to make big money, they'd go to the mines in Australia," he said.
"You can't get much shittier work than working in a mine. And why do people go there? They pay them extremely well. If you paid very high wages on a dairy farm, I think you'd get probably the best workers that you'd need, be they migrants or native New Zealanders."
Mr Lamb said many New Zealanders were working for larger corporate farms because they offered good pay and working conditions, and gave a clear career path.