Updated: May 25, 2021
There seems to be a misunderstanding in the public about why South Africa's commercial farmers reduced from 1990 onwards. Many think it is due to a white genocide or from farm murders. It was actually due to changes in commercial farming operations.
"Farming units fell from 66, 000 in 1990 to around 35,000 (2016 figure), a decline of over 1,800 units per annum for the period. On absolute numbers, white owned farms have been “failing” at a higher rate than new black farmers have been. Even these figures mask the full extent of the change increasing dominance of large scale, corporate and highly capitalised farming operations. By one estimate, just 237 commercial farm units accounted for 33% of total agricultural income in 2007 and 2,330 farm units accounted for 53% of gross agricultural income in 2005" - Dirk de Vos, Daily Maverick
Farming Portal had a great explanation: "The number of commercial farmers in this country has dropped from 66 000 in 1990 to around 35 000 today. This trend is not unique to South Africa, and results from low margins at farm-gate level. These force commercial farmers to consolidate in order to gain economies of scale. " Also, worldwide trends towards larger farms has led to commercial operations expanding by acquiring smaller rivals. This also contributed to lower amount of farmers. Link:
Also there were 1888 farm murders from 1990 to mid 2017, so that's not where the rest of the commercial farmers went (The 1888 is also not just made up of commercial farmers). Source TAU: https://africacheck.org/wp-content/uploads/2017/05/SHORT-MURDERS-ATTACKS-STATS-1990-2017-xlsx.pdf
PS: The 32,000 Commercial farmers in SA are Farmers registered to pay VAT and were recorded in the Agricultural Census in 2007. 2007 Census of commercial agriculture: http://www.statssa.gov.za/publications/Report-11-02-01/Report-11-02-012007.pdf
A more recent census has been done - see here: http://www.statssa.gov.za/publications/Report-11-02-01/Report-11-02-012017.pdf