M.J. Joubert was an assistant in the Agronomy Division of the Department of Agriculture of the Orange River Colony (now the Free State) from August 1905 to September 1906. He then received a government scholarship to study agronomy (the science of soil management and crop production) at the Ontario Agricultural College in Guelph, Canada, where he obtained the degree Bachelor of Science in Agriculture (BSA) in 1909. Upon his return to South Africa he was appointed as assistant instructor in agriculture in the Orange River Colony, from October 1909.
After the formation of the Union of South Africa in 1910 Joubert was appointed, in July 1912, as the first principal of the School of Agriculture at Glen, near Bloemfontein. Although land was obtained for the school that same year, building was delayed owing to World War I (1914-1918) and the school was completed only in 1918. Classes started the next year. Joubert remained principal to January 1924, when he was transferred to the Grootfontein College of Agriculture. There he succeeded R.W. Thornton* as principal and remained until May1929.
Joubert became a member of the South African Association for the Advancement of Science in 1911.