Sergey Kazakov, 35, punished the boy for ‘running away from home and stealing money’ by making him kneel – sometimes naked – for nine hours at a time on the grain, causing seeds to take root in his bloodied knees.
The crop had to be surgically removed under general anesthetic at a hospital in Omsk, Russia.
The boy’s mother Alina Yumasheva, 27, admitted she had approved the punishment which was inflicted on ten consecutive days in May 2019 and other times.
Kazakov also kicked the boy and pulled his hair while he was kneeling.
Yumasheva was sentenced to one-and-a-half years in prison while mastermind Kazakov was jailed for four-and-a-half-years.
The pair were fined a total of £4,825 which must be paid to the boy.
The eight-year-old had been living with his mother until her trial and now has been sent to an orphanage.
Nurse Lyudmila Sharapova told the court: ‘It is the first time in my 43 years work that I have seen such injuries.
‘The wounds were infected, the buckwheat had been embedded into his skin for several days.
‘It was horrific. The mother should beg her son to forgive her until the end of her life.
‘When I was cleaning up his wounds, he asked me: “Auntie, will you put me into a normal family now?”‘
A neighbor who saw the wounds said: ‘There was no skin on his knees, just raw meat.’
Yumasheva claimed that she and Kazakov discovered the form of punishment on the internet.
The mother told the newspaper Komsomolskaya Pravda: ‘I checked on it myself and set up an experiment.
The couple also starved the boy for up to four days at a time, claim state investigators.
Computer programming entrepreneur Kazakov told police he had inflicted the punishment once but several more deleted videos were traced on his phone, say, investigators.
The boy’s ordeal came to light when he fled the family home and pleaded with a female neighbour to get him ‘a normal family’.
The neighbour called in doctors because of the horrific wounds on the child’s bleeding knees.
However, after one month in hospital, the boy has been returned into her care, say Russian reports.
This was despite the boy pleading with his nurse in hospital: ‘Will you send me to live in a good family now?’
The child’s class teacher Olga Pidzhakova said the boy was academically bright but she believed he had been scared to complain.
‘He is a good, positive child,’ she said. ‘His mother constantly attends parental meetings, comes if I call.
‘He is always clean, and neatly dressed.
‘Neither I, nor other teachers or children were even aware that he was being bullied at home. It is only now that I find out he was simply afraid to complain to us.