Johan Steenkamp and Arnold Cloete, co-owners of the Akkerland Boerdery hunting farm, were ordered to "handover the farm's keys to the state" late last year after refusing an offer of one-tenth the land's value.
"What makes the Akkerland case unique is that they apparently were not given the opportunity to first dispute the claim in court, as the law requires," AgriSA union spokeswoman Annelize Crosby told the paper.
The owners wanted 200 million rand ($22.7m) for the land but were offered just 20 million rand. If the seizures go ahead, it would be the first time the state refuses to pay market value for land.
Since the end of apartheid in 1994, the ruling African National Congress has followed a "willing seller, willing buyer" process to redistribute white-owned farms to blacks.
That process has been slow — a 2017 government audit found white people still owned 72 per cent of private farmland in South Africa, despite making up less than 9 per cent of the population.
Amid growing pressure from the radical Marxist opposition group the Economic Freedom Fighters, the ANC made expropriation without compensation a key pillar of its policy platform late last year.
The South African government is pushing ahead with plans to change the country's constitution to make that process easier, but has targeted a number of farms for seizure "to test out" the current laws.
Under the existing constitution, land can be expropriated in exchange for "just and equitable compensation", or without compensation when "in the public interest".
The Department of Rural Development and Land Affairs has reportedly drawn up a list of 139 farms targeted for this purpose, but has refused to reveal details.
ANC spokesman Zizi Kodwa attempted to play down investor fears, saying earlier this month the proposed seizures were "tied to addressing the injustices of the past".
"Over time I think the markets as well as investors will appreciate that what we are doing is creating policy certainty and creating the conditions for future investment," he told City Press.
Civil rights group Afriforum subsequently released what it claimed to be a leaked list of 190 farms "being circulated in the department", sparking vehement denials from the government. "We don't know where they got it from," a spokeswoman said. "There is no truth to this document."
On Tuesday, AgriSA and Agbiz announced that senior ANC officials had vowed to protect property rights at "historic" meeting. AgriSA said "specific policy commitments" were made.
Those included that "no land grabs will be allowed", "the protection of productive agricultural land will remain a priority" and "property rights will remain a key priority in agrarian development".
In a media release, the AgriSA said "all agreed that those factions who are purposefully polarising society with regards to land question, should be resisted".
Speaking to News24, AgriSA chief executive Omri van Zyl, said the discussion did not directly address expropriation without compensation.
"It was a general discussion which has laid the foundation for the future," he said. "It is pretty clear the party is worried about the impact of the land debate on the private sector and investors."