Agricultural practices and water quality. Edited by Ted L. Willrich and George E. Smith. Willrich, Ted L., ed. Smith, George Edward, 1913- ed. Iowa State University. Water Pollution. Agriculture. TD420 .A33 628.168 WIA "Result of a conference, The role of agriculture in clean water, held at Iowa State University, Ames, Iowa, November 18-20, 1969." Includes bibliographies. Ames, Iowa State University Press [1971, c1970] [1971, c1970] 1971 Text xxvii, 415 p. eng