The Edina soil series of southeastern Iowa and northern Missouri are soils of relatively flat topography and poor internal drainage. The need for research data on the feasibility of drainage (both surface and subsurface) on the Edina soils was recognized at the time experiments were begun on the Southern Iowa Experimental Farm, Davis County, Iowa. The yield response of corn to surface drainage by bedding was summarized and reported by Beer et al.³ in 1961. Since initiation of the subsurface drainage experiment in 1949, data on crop-yield response to tile drainage have been collected. The purpose of this bulletin is to present the results of this study as related to the effects of tile drainage on crop yields, with the emphasis on corn, during the period of record. The nature of tile discharge during the growing seasons from 1951 to 1963 also is presented.