The South Australian government's controversial changes to land tax have passed state parliament.

The new measures won the support of both houses on Thursday after further concessions ensured the backing of the Greens in the upper house.

The reform package delivers $189 million in tax cuts to investors over three years, including tax relief for thousands of smaller “mum and dad” investors.

It also slashes the top land tax rate from 3.7 per cent, the highest in the nation, to 2.4 per cent.

Treasurer Rob Lucas said the changes would deliver a more competitive, investment-attracting environment for the state, that would drive significant jobs and economic growth.

“This is a once-in-a-generation opportunity for significant land tax reform that will benefit South Australians now and into the future,” Mr Lucas said.

“This reform package not only massively slashes the top land tax rate to create a more competitive business and investing environment for South Australia, but delivers a far more equitable and fairer land tax system.”

The government first unveiled the land tax reforms in the June state budget but the initial proposals were heavily criticised by business groups and investors.

Since then it has revamped the legislation several times.

In the most recent changes, it agreed to include a $25 million transition fund to help small investors who might be hit by the tax changes.

On Thursday, the treasurer also agreed to provide more cash for the maintenance of public housing and more for emergency accommodation to appease the Greens.

But the government has kept one of the most controversial features, effectively closing a loophole which allowed some large investors with multiple holdings to avoid paying any land tax.

The aggregation provisions stop people using complex ownership structures in order to reduce or eliminate their tax bill.