The 19-year-old signed a new deal with the Premier League club at the end of the past season, having played three EFL Trophy games.
Ballard has played under-18 and under-23 games for the Gunners, and was called into the Northern Ireland squad for the first time this spring.
“It’s my first loan so I’m nervous but really excited,” Ballard said.
He told the club website: “I think the stadium is really impressive – I played a lot at Boreham Wood last year [for the youth side] and this is leaps ahead of that. The fanbase is a lot bigger and I can’t wait to play in front of them.”