Saskatchewan gets a failing grade for the way it collects potash royalties, a report from the University of Calgary says.

Economist Jack Mintz says this province's rules are "horribly complex" and "a mess" and need an overhaul.

"It is possible to develop a far simpler and efficient royalty structure without impairing the incentive for potash producers to invest in Saskatchewan," the report Mintz co-authored with Duanjie Chen and released Friday says.

"We highly recommend a simple structure with a revenue-based royalty that would operate as a creditable minimum tax and a single-rate profit tax on rents — income in excess of the economic cost of production."

The report doesn't recommend an across-the-board increase in potash royalty rates.

Asked about the U of C report the day before, Premier Brad Wall said he appreciates the interest, but the potash industry creates thousands of jobs in Saskatchewan and he's not planning to tinker with the rules.

Potash is an important cash cow for the province, with royalties putting hundreds of millions of dollars into the treasury every year.