At tea, England -- who won the toss -- were 113 for three with Boult having removed both skipper Alastair Cook and the obdurate Jonathan Trott during the second session.
The accurate Boult had figures of two for 23 off 15 overs at the interval.
Ian Bell was 18 not out and Joe Root, in his first Test on home soil, unbeaten on nought following a session where England took 57 overs to score 27 runs and lost two key wickets in the process.
Although blue skies overhead on a sunny day promised ideal conditions for batting, an outfield relaid after the Olympic archery tournament at Lord's last year prevented several well-struck shots getting to the boundary.
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England got off to a slow start after Cook won the toss with only two boundaries in the morning session.
Nevertheless, Cook and fellow opener Nick Compton were rarely troubled until the introduction of Bruce Martin, the sole specialist spinner in the side after he was preferred to Doug Bracewell.
And 43 for one should have become 48 for two when the 33-year-old Martin, in only his fourth Test and first outside New Zealand, had Trott driving early but dropped the caught and bowled chance.