Yield response of corn in a planosol soil to subsurface drainage with variable tile spacings /
Beer, C. E.(Craig Eugene),1927-author.
Johnson, H. P.(Howard P.),author.
Shrader, W. D.(William Duncan),author.
Iowa State University.Agricultural and Home Economics Experiment Station.
Iowa State University.Department of Agricultural Engineering.
Iowa State University.Department of Agronomy.
Title from front cover.
Includes bibliographical references.