Christopher Hill, 17, from Gorebridge, Midlothian, met up with friends at his local football pitches on 31 August 2009, before heading towards Turniedykes Farm in Pathhead.
At Edinburgh Sheriff Court today (Thur) he pled guilty to culpably and recklessly setting fire to the hay bales, which resulted in them being destroyed.
Hill, who is currently studying for his higher qualifications, was 16 at the time, and claims he lit the plastic wrapping around the bales in order to gain access to the hay inside.
Fiscal Depute Dev Kapadia said: “It is understood that the damage to the crop cost the owner £4,000.
“A group of youths met and went to climb on the said bales of hay, when it was suggested that a fire should be started.
“The accused then pulled a lighter from his pocket and set fire to the plastic wrapping around it, which unfortunately caught on quickly and resulted in the hay bale itself going up in flames.
“The fire spread quickly amongst the other bails and all of the witnesses and the accused tried to put it out but realised that the scale of the fire was too much for them.
“They fled the scene and one of the witnesses told his mother, who notified the police and traced Mr Hill.
“He was taken to Dalkeith Police Station where he admitted that one of the witnesses had wanted to burn plastic on the bails and he accepted that he set fire to the plastic.”
Defence solicitor Mark Hutcheson said: “Mr Hill was one of a number of children simply playing on the hay bales.
“A suggestion was made to burn through the plastic to get access to the hay so they could play with it, so he did so.
“He knows that this was stupid on his part.
“When they realised the extent of the flames they tried in vain to stamp it out but it had already taken hold.
“My client has been in no trouble since, and realises the stupidity of his actions and is willing to face the consequences.”
Sheriff Alistair Noble said: “There is no dispute that it was complete stupidity from either the Crown or the defence.
“I am taking into account your young age and I am going to defer sentence until six months from now to allow you to show me you can stay out of trouble.
“If you do, you will be dealt with leniently.”
Sheriff Noble ordered him to appear at court on 6 July this year.