A visa scheme for migrant farm workers was in place in some form between 1945 and 2014. Participants were typically students from European countries.
The most recent incarnation, the Seasonal Agricultural Workers Scheme, was restricted to Romanian and Bulgarian citizens from 2008. It was then scrapped altogether in 2014. The government considered that demand could be met by EU workers allowed to come to the UK without visas, particularly from Eastern European countries.
https://commonslibrary.parliament.uk/research-briefings/cbp-9665/