Club president Michael Hore said Johnston was a capable fullback and wing, and also played at halfback when needed.
''He was a good club man. He was green and black through and through.
''He was one of those good buggers, I suppose you could say.
"He was a good man around the club as well. If you could have more people like him in your club, it would be great. He would always be there, being a ball boy, even before he started to play for the seniors.''
Johnston played all of his junior rugby for Maheno and was part of the club's senior side for ''three or four seasons'', Hore said.
He played for Maheno when it won the Citizens Shield in 2016, a famous win for the club which finished with the wooden spoon the year before.
Hore said the club's senior team members had a ''get-together'' at the club on Thursday night to pay tribute to their team-mate.
''It hit a few of the boys pretty hard.
''Everyone was obviously in a bit of shock. We sort of celebrated him really. It's still pretty fresh ... We're just there for the family and anything they need.''
A WorkSafe spokeswoman said Johnston's death was the 17th farm fatality in New Zealand this year and the fifth this month.