Although the parents had other children, including another adopted daughter, the court heart that the 12-year-old was treated differently to the rest of the family.
The girl was often beaten with various objects including a tennis racket and rubber hose and was made to sleep in a locked shipping container during winter with no blankets.
The child was seen by neighbours running laps of the paddock and standing alone in the rain for hours on end. She was also forced to wash in a bucket outside.
During the trial at the District Court in Perth, the girl's teachers revealed that she would frequently come to school smelling of urine.
The mother claimed that she had wet herself on purpose and had been forced to wear the soiled underwear as punishment.
The abuse was only reported to authorities by a friend's father after she visited their home smelling of urine.
While Judge Alan Troy accepted that the girl has caused difficulties for the couple, he condemned their abusive behaviour, insisting they should have contacted authorities instead.
'You were entrusted to look after her. You must have known she was suffering emotional abuse and neglect,' he said.
He added that the shipping container that she was kept in during the coldest months of the year was 'unfit for human habitation'.
The pair were sentenced to four years in jail and will have to serve at least half of the term before being considered for release.