It contained household rubbish and water from recent rain.
The property's owner, Kelvin Reed, said the family who lived there worked for him on the 259ha dairy farm.
"It was a little boy. He wandered off and got into a rubbish hole with a bit of water in it,'' Mr Reed said.
"You know with kids - they've got no danger, they've got no fear. Water is an attraction.''
It had been raining steadily for the past few days, Mr Reed said.
The boy's father had been out working on another farm at the time and the boy was thought to have been at home with his mother and sister.
"It's obviously a shock. It always is with kids.''
Senior Sergeant Richard McPhail said the hole was not a great distance from the house.
"The child was at a residential home and has managed to get outside and ended up in a hole which had water in it, which is a really tragic situation.''
Victim Support had been offering support to the family.
The boy's death had been referred to the coroner while the police and Department of Labour investigation continued.
