A late Gareth McLeary goal wasn't enough for the Royals, after Elliott Bennett had earlier scored twice in three minutes.
"We know Norwich are very good on crosses and set plays and unfortunately we just weren't able to deal with one set play," Adkins said.
"We know they're very good on crosses and set-plays, that's predominantly where their goals have come from this season.
"There was a 10-15 minute spell when Norwich's tails were up and we didn't deal with the physicality of the balls into the box. Ultimately that cost us the game."
The result means that Reading remain at the foot of the Premier League.