The offences took place in Waiouru between September 2011 and May 2012, while Manning was an instructor.
Seven of the charges he was guilty of were doing an act likely to prejudice service discipline, which related to Manning having sex with two recruits.
He was also found guilty of indecently assaulting a third recruit.
He was found not guilty of five charges relating to sexual violation and inducing a sexual connection by threat.
Judge Blackie said the sentence was to deter others from conducting themselves in the same way as he had.
"The policy on fraternisation is a common knowledge and was a fundamental understanding of anyone in command, and you were in command."
Manning would groom female recruits with a view to making sexual advances for his own sexual gratification, Judge Blackie said.
"As new recruits you would have expected them to trust you, to look up to you, to obey you."
Earlier today the court was told Manning had been honoured for his actions during service in Afghanistan.
Captain Mathew Marinovich, who spoke as a character witness for Manning, said the bombardier had served in Afghanistan and East Timor and performed to a "high standard".
In a statement, Chief of Army Major General Dave Gawn condemned the behaviour of Manning.
"His conduct has been contrary to the training given to him as an instructor of future soldiers and to the values of all of the New Zealand Defence Force.
"The New Zealand Defence Force expects high standards of behaviour and integrity from its personnel and has a duty of care to each of them. Conduct that creates an unsafe environment for men and women, both uniformed and civilian, will not be tolerated."
He said the NZDF ensured it investigated the allegations at length immediately once they were brought to the attention of military police, and it was the express wish of the complainants that these matters were dealt with by the military.
"Considerable change has been enacted at Waiouru and across the Defence Force to ensure this scenario will not recur."
Manning was awarded the Distinguished Service decoration in the 2009 New Year Honours list because of an incident in Afghanistan where he intervened and halted a violent incident between two local police officers.
There is a 30-day period in which Manning can appeal.
