Chrisna Bootha
The Proteas took just three moves to get onto the scoreboard and raced into the lead at the Good Hope Centre, in Cape Town, on Monday night.
The visitors initially looked shell-shocked, but began to fight back as the first quarter continued, narrowing the gap to just four goals.
The hosts led 15-11 after the first 15 minutes.
But the Proteas pulled away from the visitors, who were unable to narrow the gap until the final quarter.
South Africa won the second quarter by 17 goals to nine, and the third by 12 goals to eight.
The exciting young player Bongiwe Msomi, who came on at the end of the first quarter, had an outstanding game.
'Surprise'
Others to shine included player of the match Amanda Mynhardt and goal shooter Chrisna Bootha, who achieved 80 % success, scoring 41 goals from 51 attempts.
"They were very physical, and that took us by surprise," said Northern Ireland captain Gemma Gibney.
"They were stronger and faster than we were, and we were a bit heavy-legged, because seven players in our team had played in the World University Netball Championships last week."
"It was a great experience for Northern Ireland," said coach Jill McIntosh.
"Northern Ireland need more of this sort of competition. I think they found it a bit daunting. Northern Ireland are by no means down and out."
'Enforced errors'
Proteas' captain Amanda Mynhardt said she was pleased with the team's performance, although she believed they could do even better.
"We made a number of unforced errors and we will be working on those," she said.
"Northern Ireland are like little Jack Russell terriers – they are on you the whole time. We can never be complacent against them, but we will learn from our mistakes tonight."
Coach Elize Kotze said she was happy she had been able to ring the changes and give every member of the squad a game. "We have enough depth and versatility to be able to do that," she said.
"We started the match with most of the team that beat Jamaica, but I had the luxury of being able to bring on replacements. I don't like to be too predictable." – Sapa