South Australia 3 for 134 (Drew 51*) trail New South Wales 9 for 447 dec (J Edwards 138, Hackney 78, Dwarshuis 60*, McAndrew 6-97) by 313 runs
NSW declared midway through the middle session at 9 for 447, with South Australia reaching 3 for 134 at the close on day two.
Daniel Drew (51no) was leading the way for South Australia. The other major contribution came from opener Kelvin Smith, who hit a confident 46 in his first Shield match for four years before missing a cut against Chris Green.
Henry Hunt had early become a maiden first-class wicket for Ryan Hadley while Nathan McSweeney was bowled when he shouldered arms at Chris Tremain.
Allrounder Edwards led the way for the inexperienced NSW side with an innings of 138 that included 20 boundaries and a six.
The 22-year-old's second Shield century eventually came to a close after 179 balls with a catch on the point boundary off the bowling of Nathan McAndrew.
Edwards and fast bowler Ben Dwarshuis were rarely troubled on the Karen Rolton Oval pitch in their 127-run stand for the eighth wicket. Dwarshuis ended unbeaten on 60, having notched his first half century.
It was a day of career-highs with the NSW-born McAndrew returning 6 for 97, securing his maiden first-class six-wicket haul in the process.
South Australia's hopes of reaching the final ended in last week's penultimate round, while NSW are seeking to avoid a first-ever winless campaign in a 10-match season.