Bill Roddie is said to have effectively blocked access to the charity's stables at Bannockburn, near Stirling, by digging out pothole repairs and putting down boulders to prevent visitors driving around them.
Worried parents and fundraisers now believe the developer, who has a conviction for fraud, simply wants to shut down the centre, which is just 100 yards from his Scots Baronial mansion.
Carol Simpson, manager at Bannockburn Riding for the Disabled, said: "Parents just assume our landlord wants us off the site, which we have leased for another 11 years before a break and where we have invested hundreds of thousands of pounds.
"We have tried repairing the road but estate workers simply dug out the hardcore we put in the potholes and put fences and bounders beside them so nobody could drive around them.
"We would like to ask the landlord to please let us keep this centre and let the riders continue."
Mr Roddie and the centre, which was on the estate when he bought it, have been in arbitration over who is responsible for repairing the road, which also provides access to a timberyard used by heavy lorries.
The potholes - although making the road impassable for most vehicles other than 4X4s - would be relatively easy to fill and the riding centre said it has been willing to do so.
The riding centre closed "on grounds of safety" a few weeks ago but has partially reopened, ferrying clients up its road in an old Land Rover. "We are working at about one-third capacity," said Ms Simpson. "We can't take minibuses or adapted cars for disabled people up the road so many of our clients can't make it."
Struggling to get to her classes yesterday was Gemma Lumsdaine, from Monifieth near Angus, who makes the journey regularly as she aims to compete in dressage at the 2020 para-Olympics.
The 16-year-old has cerebral palsy and uses a wheelchair. She depends entirely on the specialist coaching at Bannockburn. "They are fundamental," she said. "I couldn't do without their support."
Her mother, Sally Lumsdaine, has been driving Gemma to the centre for two years. The road has become a real problem for her low-slung people carrier, which takes Gemma's wheelchair, and her car has had to be repaired twice.
Dorothea Jamieson also takes her daughter to the centre once a week. Debbie, 42, has Down's Syndrome and is a veteran of the Special Olympics.
"The riding is her life, the highlight of her week," Mrs Jamieson said, enjoying a coffee in the centre's cafe. "She has been coming here for 16 years and loves it."
Bannockburn is Scotland's main centre of excellence for disabled riding, whether it is for therapy or, like Gemma, for competition. Its closure or relocation, all clients said, would be a disaster.
Parents have recruited Stirling MSP Bruce Crawford - an old foe of Mr Roddie from right-to-roam rows - to their cause.
Mr Crawford, visiting the centre yesterday, said: "I would ask the landlord to act in a reasonable manner and sit down and discuss how the current impasse can be overcome.
"The Riding for the Disabled Association has made a huge investment in infrastructure and obviously it would be reluctant to even consider moving."
Mr Roddie, who is understood to be trying to market parts of his estate, was unavailable at his home yesterday to comment.