Proceedings of a symposium - Ferre, Frederick,; Curtis, Stanley E.,; Comstock, Gary,; Blatz, Charles V.,; Freudenberger, C. Dean,; Ruehr, Thomas A.,; Hartel, Peter G.,; Skipper, Horace D.,; Paxton George, Kathryn,; Vorst, James,; Kral, David M.; Kasper, Pamm, (Soil Science Society of America ; American Society of Agronomy ; Crop Science Society of America, 1994)