Top scorer for the past three seasons, Holt clinched a three-year deal with the Canaries last week, taking him to 2015.
"It was a good boost for the club just before pre-season started. The big man's staying, so it's really good news," said Martin.
"He had a lot of suitors because of the season he had, well, the last three years he's had, and he's a big character in and around the dressing room as well. It was important for us to keep him and thankfully the management and the board have managed to do that."