Earlier, South Africa captain Graeme Smith called in his players after A.B. de Villiers fell for 67 soon after the break and Robin Peterson was bowled for 5.
De Villiers had led South Africa to the brink of a 300-run lead before he fell to Chris Martin for his 30th Test half-century, while Peterson cracked one four over mid-wicket before also being bowled by Martin trying another big shot.
New Zealand’s bowlers had struck early on the second day, but their vastly-improved effort from the first day still could not stop the top-ranked South Africa from forging further ahead.
The Black Caps briefly returned the match to a more normal — if not yet even — contest in the first session after South Africa was 252-3 overnight, removing Alviro Petersen for 106 in the day’s second over, Faf du Plessis for 15 in the 10th and Dean Elgar (21) just before lunch to slow South Africa’s runaway start.
De Villiers still ensured South Africa built steadily on its one-sided dominance of the first day, leading the Proteas to 335-6 at the lunch break with the home team’s third half-century alongside Petersen’s century.
Morning rain yesterday gave the beleaguered Black Caps a boost on a Newlands pitch that already had some cracks for the bowlers to exploit and Trent Boult’s 3-78 was the best in a vastly improved effort from the tourists.
Their mini-fightback, when they took 3-83 in the session, was too late to save this Test, but the much-criticized Black Caps might be buoyed by the small signs, if their limp batting lineup could only stand up to the top-ranked Test side’s feared quick-bowling attack.
That appeared again unlikely after just one Steyn over.
Earlier, century-maker Petersen was prevented from doing any more damage to the tourists’ flagging morale when he was beaten by an in-cutter and edged left-armer Boult’s first delivery of the day onto his stumps.
Du Plessis pushed at a Chris Martin ball that swung away from him and was caught in the gully as South Africa slipped to 281-5. Dean Elgar finally fell caught behind to Boult, having survived what looked like a good LBW appeal from the same bowler shortly before.