In 1891 Warington was appointed by the committee for the Lawes Agricultural Trust to give six lecture in the United States before the Association of American Agricultural Colleges and Experimental Stations at Washington, D.C. from August 12 to 18, 1891.[6] The lectures dealt mainly with the subject of soil nitrification, based upon his own research at Rothamsted. When he returned to England, he did research at Lawes's Millwall laboratory. He was appointed in 1894 as an examiner in agriculture for the science and art department of the University of Oxford[2] and was for three years, from 1894 to 1897, the Sibthorpian professor of rural economy[3] at the University of Oxford.[1]