ADVANCES IN AGRONOMY VOLUME V This Page Intentionally Left Blank ADVANCES IN AGRONOMY Prepared under the Auspices of the AMERICAN SOCIETY OF AGRONOMY VOLUME V Edited by A G NORMAN University of Mkhigan, Ann Arbor, Michigan ADVISORY BOARD J E ADAMS G W BURTON J E GIESEKING I J JOHNSON RANDALL JONES C E MARSHALL R Q PARKS K S QUISENBERRY 1953 ACADEMIC PRESS INC., PUBLISHERS NEW YORK Copyright 1953, by ACADEMIC PRESS INC 125 EAST2 STREET ~ ~ NEW YORX 10, N Y A11 Rights Reserved N o part ol this book may be reproduced in any form, by photostat, microfilm, or any other means, withozlt written permissiolt from the publishers Library of Congress Catalog Card Number : (50-5598) PRINTED IN THE UNITED STAlTB OD' AMERICA 'CONTRZBUTORS TO VOLUME V F E BROADBENT, Associate Professor of Soil Microbiology, Department of Agronomy, Cornell University, Ithaca, New Pork M B DAVIS,Chief, Horticulture Division, Central Experimental Farm, Department of Agriculture, Ottawa, Canada C H GOULDEN,Chief, Cereal Division, Experimental Fwm Service, Department of Agriculture, Ottawa, C a d I; W HURLBUT, Chairman, Department of Agricultural Engbaeerilzg, University of Nebraska, Lincoln, Nebraska M L JACKSON, Professor of Soils, University of Wiscomin, Madison, Wisconsin R W LEUKEL,Plant Pathologist, Division of Cereal Crops a w l Diseases, Burea