|LV= County Championship Division One, Ageas Bowl|
|Nottinghamshire 301-6: Hales 136no, Mullaney 66|
|Hampshire: yet to bat|
|Nottinghamshire 3 pts, Hampshire 2pts|
Nottinghamshire's Alex Hales became the first batsman to reach 500 first-class runs for the season with a fluent century against Hampshire.
The 26-year-old followed up his career-best 236 against Yorkshire with 136 not out, including 24 fours.
Hampshire used the cloudy conditions to stay in contention, but Nottinghamshire reached the close on 301-6.
Opener Steven Mullaney (66) shared 84 with Hales and Will Gidman (22 not out) a further unbeaten 50 late in the day.
Hales came to the wicket at 66-1 in the 23rd over after spinner Danny Briggs bowled Brendan Taylor (24) with his first ball of the match.
|How Hales was first to 500 first-class runs in 2015|
|April 7-9: 46 and 83 v Loughborough MCCU||April 12-15: 0 and 37 v Middlesex|
|April 19-22: 236 and 2 v Yorkshire||April 26-29: 136no v Hampshire|
Mullaney went to his fifty from 138 balls and hit nine boundaries in all before he chased a wide one and was caught at slip by the diving Adam Wheater, handing Sean Ervine his 200th first-class wicket for Hampshire.
Hales opened up either side of tea with a succession of offside drives, despite losing James Taylor second ball after the resumption, caught at slip trying to sweep Liam Dawson.
The number three reached three figures from 156 balls, even though Hampshire continued to make inroads, as Samit Patel, Riki Wessels and skipper Chris Read all fell relatively cheaply.
Just as the hosts sniffed a swift end to the visitors' innings, Will Gidman (22 not out) joined Hales to steady things before the close.
Nottinghamshire batsman Alex Hales:
"Its been a good day for me and the team. We would have ideally liked to have fielded first, there was a little bit in the wicket, but once the innings progressed it got a bit easier to play.
"It is a purple patch, I'm really enjoying my cricket at the moment. I've got to not get complacent and keep churning out runs when I'm in this form.
"The plan is to bat as long as we can tomorrow and push 350 or 400 and get those extra points.
"If we come out and stick the ball in the right areas, there is still plenty in the wicket to get a result."
Hampshire first-team coach Dale Benkenstein:
"I think they have the advantage, we would have liked to have bowled them out for under 300.
"There was enough in the wicket, but Hales batted very well. We bowled well in patches. I don't think we put the ball in the right areas for long enough.
"Similarly to the Sussex game, we had a lot of bad luck, a lot of balls just went past the edge.
"We would have batted if there was a bit of sun around. I still think that the conditions were as good as it gets for our seam bowlers."