The home side led 10-0 at the break and pulled away in the second half, with swift running fullback Bronson Tumai helping himself to three tries.
The win, though, was set up by a strong, hard-driving Southern pack, which got the better of its opposition and recycled the ball efficiently, despite the difficulties of playing on a slippery surface.
Its scrum was also in charge for most of the game, and the loose forward trio of Dave Kenny, Simon Grant and Shaun Tauti was never far from the ball.
The home side also possessed the more dangerous backline and managed to find holes in the Central Otago defence with some straight and hard running.
Southern coach Willis Paterson said he was really happy with the win, and the way it had been constructed.
"I thought our forward pack went together well as a whole and a couple of old guys in the backline, Sam Young and Blake Korteweg, played really, really well.
"We managed to get everyone on bar one from the bench and they all contributed," Paterson said.
Central Otago had won the cup last year but never looked likely on a chilly South Otago afternoon.
The first 20 minutes of the game was a testing-out period for both teams during which Young and Central Otago first five-eighth Thomas Huddleston missed penalty shots at goal.
But Young got his side on the board after 25 minutes, and then on halftime the home side scored its first try.
After a scrum near the line it moved the ball through three phases and big centre Korteweg dived over near the corner. Young struck the conversion sweetly.
Three minutes into the second half Tumai had the first of his hat trick. He rather selfishly ignored unmarked winger Sam Wyber outside him but still had enough strength to score.
Just over 10 minutes later he was in again after a nice chip kick from Young.
Then, with 15 minutes to go, South Otago second five-eighth Lachie Moore wrestled the ball free on his own 22m line and sprinted 30m.
He then kicked ahead and Tumai won the race to the ball.
Central scored its only points with eight minutes remaining when veteran prop Lance Davies barged over after a series of charges at the line by the visiting team.
The home side had the final say when flying winger Tyler Bichan was too quick for the defence after those inside him had forced a turnover.
The win completed a clean sweep for the Southern teams, which won the other three games played yesterday.
It won the development game 12-8, the under-14 match 20-7 and the under-18 game 20-19.
Topp Cup scores
- Southern Region 34: Bronson Tumai 3, Blake Korteweg, Tyler Bichan tries, Sam Young pen, 3 con
- Central Otago 5: Lance Davies try
- Halftime: 10-0.
Three to impress
- Fullback Bronson Tumai: The Southern fullback helped himself to three tries and impressed with some nicely timed entries to the backline and running some nice angles.
- Halfback Jamie Brown: The young man from Kaitangata showed a nice pass and a real burst of acceleration to set up Tumai's first try. He also possessed a solid kicking game.
- Hooker Angus Gibbons: The Central Otago rake never stopped running, always making the advantage line, often taking on two or three men.
