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 3 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, Bureatcan be identified. The use of implements that cover the ground more quickly and with less expense than the plow without impairment of yields has greatly reduced the costs of growing wheat and has insured greater timeliness in seedbed preparation and seeding. d. Fallow in the Great Plains. Some wheat was grown on fallow in the more arid sections of the Plains at the beginning of the century, but the practice was slow in becoming established partly because farmers were loathe to believe that they could not grow a crop every year. Also, frequent cultivation with a disk or harrow greatly encouraged soil blowing. Fallowing was not as complete an insurance against crop failure as many believed or to the extent that it was on the semiarid lands of the Far West. I n a very severe drought, wheat on fallowed as well as on cropped land might be a complete failure. Chilcott compared fallowing to fire insurance that afforded protection against small fires but not against a general conflagration. TABLE I1 Estimated Acreage in Summer Fallow for Selected States and Periods Period 1928-1932 1939 1942 1943 1944 1951 t i Seven Western States, * millions of acres Ten Great Plains States, t millions of acres Total seventeen states, millions of acrea 5.5 5.4 5.4 5.1 4.6 5.6 5.3 15.9 14.4 12.0 10.2 17.9 10.8 21.3 19.8 * Washington, Oregon, Idaho, California, Nevada, Utah, and Arizona. t Montana, Colorado, Wyoming, New Mexico, North Dakota, South 17.1 14.8 23.5 Dakota, Nebraska, Kansas, Oklahoma, and Texas. t t Data for 1951 from "Agricultural Capacity to Produce," U.X. Dept. Agr. Inform. BuU. 88, June 1952. 36 S. 0. SALMON, 0. R. MATHEWS, AND R. W. LEUKEL Interest in fallow began to increase in the twenties and was especially great during the drought in the mid-thirties. The extent to which fallow has been used at various times in seven Western States and in the ten states of the Great Plains, as reported by Johnson (1949), is shown in Table 11. The greater portion of fallowed land in the United States is sown to winter wheat, which shows more response to fallow than do most other crops. Spring wheat also is grown on fallow, chiefly in the northern and drier portion of the Great Plains spring wheat area and to a lesser extent in the Columbia River basin,