ADVANCES IN AGRONOMY VOLUME 20 CONTRIBUTORS TO THIS VOLUME W. H. ALLAWAY GLENNW. BURTON MICHELP. CESCAS ROY G. CREECH LAWRENCE J. GRAY V . A. JOHNSON W. D. KEMPER I. C. MAHAPATRA S. R. OLSEN WM. H. PATRICK, JR. JERREL B. POWELL J . W. SCHMIDT ROY W. SIMONSON EDWARDH. TYNER ADVANCES IN AGRONOMY Prepared under the Auspices of the AMERICAN SOCIETY OF AGRONOMY VOLUME 20 Edited by A. G. NORMAN The University of Michigan, Ann Arbor, Michigan ADVISORY BOARD J. P. MARTIN R. R. DAVIS F. A. HASKINS J . W. PENDLETON W. D. KEMPER W. A. RANEY ACADEMIC PRESS 0 N e w York and London COPYRIGHT^^ 1968, BY ACADEMIC PRESS,INC. ALL RIGHTS RESERVED. N O PART O F THIS BOOK MAY BE REPRODUCED IN ANY FORM, BY PHOTOSTAT, MICROFILM, OR ANY OTHER MEANS, WITHOUT W RI TTEN PERMISSION FROM T H E PUBLISHERS. ACADEMIC PRESS, INC. 1 I I Fifth Avenue, New York, New York 10003 United Kingdom Edition published by ACADEMIC PRESS, INC. (LONDON) LTD. Berkeley Square House, London W . l LIBRARY OF CONGRESS CATALOG CARDNUMBER50-5598 P RI N TED IN T H E U N I T E D STATES O F AMERICA CONTRIBUTORS TO VOLUME 20 Numbers in parentheses indicate the pages on which the authors’ contributions begin. W. H . ALLAWAY ( 2 3 5 ) , Director, Plant, Soil & Nutrition Laboratory, Soil and Water Conservation Research Division, Agricultural Research Service, United States Department of Agriculture, Ithaca, New York GLENNW. BURTON(49),Research Geneticist, Crops Research Division, Agricultural Research Service, United States Department of Agriculture, Georgia Coastal Plain Experiment Station, Tifton, Georgia MICHELP. CESCAS( 1 5 3 ) , Assistant Professor, Department of Soil Science, Lava1 University, Quebec, Canada ROYG . CREECH( 2 7 5 ) , Associate Professor of Plant Breeding, Department of Horticulture, College of Agriculture, The Pennsylvania State University, University Park, Pennsylvania LAWRENCE J. GRAY( 1 5 3 ) , Physicist, Ocean Technology Department, United States, Naval Undersea Warfare Center, Pasadena, California V . A. JOHNSON ( 199), Research Agronomist, Crops Research Division, Agricultural Research Service, United States Department of Agriculture, Agricultural Experiment Station, Lincoln, Nebraska W. D. KEMPER(91), Research Soil Scientist, Soil and Water Conservation Research Division, Agricultural Research Service, United States Department of Agriculture, Professor, Department of Agronomy, Colorado State University, Fort Collins, Colorado I. c. MAHAPATRA ( 3 2 3 ) , Agronomist, Central Rice Research Institute, Cuttack, (Orissa), India S . R. OLSEN(91), Research Soil Scientist, Soil and Water Conservation Research Division, Agricultural Research Service, United States Department of Agriculture, Colorado State University, Fort Collins, Colorado WM. H . PATRICK, JR. ( 3 2 3 ) , Professor of Soil$, Agronomy Department, Louisiana State University, Baton Rouge, Louisiana JERREL B . POWELL(49), Research Geneticist, Crops Research Division, Agricultural Research Service, United States Department of Agriculture, Georgia Coastal Plain Experiment Station, Tifton, Georgia J. W . SCHMIDT ( 199), Professor ofAgronomy, Department ofAgronomy, University of Nebraska, Lincoln, Nebraska V vi CONTRIBUTORS TO VOLUME 20 ROY W. SIMONSON ( I ) , Director, Soil Class$cation and Correlation, Soil Conservation Service, United States Department ofAgriculture, Hyattsville, Maryland EDWARD H. TYNER ( 1 53), Professor of Soils, Department of Agronomy, College of Agriculture, University of Illinois, Urbana, Illinois PREFACE This is the twentieth volume of this serial publication. Those who had a part in what seemed to be an uncertain venture in 1948 can take some pride in its acceptance and feel satisfaction i