MORE than 4 per cent of Australian rural land changes hands each year.

This is according to an Australian-first study into farm ownership patterns from 2004 until 2008, conducted by the Rural Industries Research and Development Corporation.

One of the report's authors, University of Sydney Associate Professor Bill Pritchard, said the turnover rate was higher than expected.

"Four per cent each year might not sound like a lot, but if you think it over five years it means 20 per cent of all the land has changed hands,'' he said.

The study also provided a benchmark that future studies could use to track foreign investment, corporate farming, mining uses and impacts of water policies.

"The report is based on 2008 data so it pre-dates the more recent high profile sales involving foreign buyers but there is potential for this data to better inform that debate in the future,'' Prof Pritchard said.

More research was needed, he said.

The study shows there was "a much greater diversity, and complexities, of interests in rural land than in previous decades''.

"The idea that Dad and Dave farmers are the major entity holding land is no longer true.''

The study found two major trends in land ownership changes - neighbours buying each other out in the traditional, broadacre farming regions and in more populated areas, a range of non-agricultural demands drove a higher rate of land turnover.

The Federal Government's announcement that it would introduce a register for foreign investment would be a "very difficult task'' to achieve, Prof Pritchard said.

This was because the current databases did not provide enough information about the true ownership of landholders, he said.

"The work we've done will help that process but it is going to be very labour-intensive work, and the register won't be as simple as ticking a box,'' he said.