Theodore G W ('Theo') Reinecke, agricultural chemist, was the son of Daniel Michael Reinecke and his wife Anna Maria, and a brother of the geologist Leopold Reinecke. After matriculating in 1903 he continued his studies at Rhodes University College, Grahamstown, and was awarded the degree Bachelor of Arts (BA) in science by the University of the Cape of Good Hope in 1907. Meanwhile he had also passed the university's Survey Certificate Examination in 1905. Early in the next year he was appointed as an assistant in the Department of Chemistry of the South African College, Cape Town, a post from which he resigned at the end of 1909. During 1908 he was responsible for meteorological observations made at the second order meteorological station at the college. On 1 February 1910 he entered the civil service of the Transvaal Colony (which became part of the Union of South Africa a few months later) and was employed at the Agricultural School in Potchestroom, where he was appointed as lecturer in chemistry on 1 April 1912. That year he published an article on 'Co-operative manurial experiments on lucerne' in the Agricultural Journal (Union of South Africa). This was followed by a paper on 'The manuring of Transvaal soils' (Department of Agriculture, Bulletin No. 81, 1915; 2nd ed. 1919).
From Potchefstroom Reinecke went to the University of Illinois in the United States, where he was awarded the degree Master of Science (MSc) in 1917. Upon his return to South Africa that same year he was appointed as lecturer in chemistry and acting principal of the School of Agriculture at Elsenburg, near Stellenbosch. At this time World War 1 (1914-1918) was in progress and in 1918 Reinecke was appointed to commissioned rank in the Union Defence Force. That same year he was appointed principal at Elsenburg and remained in that position to 1920. During these years he participated also in crop and pasture research at the school. In 1929 he succeeded G.J. Bosman* as head of the Glen College of Agriculture, near Bloemfontein, where he remained to 1934. During this period he wrote an article on 'Africander cattle' for Farming in South Africa (1933). During the early nineteen-forties he was the Director of Native Agriculture.
Reinecke was a member of the South African Association for the Advancement of Science by 1910. His membership seems to have lapsed during World War 1, for it was renewed in 1917. He was married to Theunissina Alberta ('Tienie') Moll.