ADVANCES IN AGRONOMY VOLUME 33 CONTRIBUTORS TO THIS VOLUME R. W. ARNOLD F. H. BEINROTH R. J . BURESH F. B . CADY M. E. CASSELMAN MARLING . CLINE G . D. FARQUHAR R. J . HAYNES ERNESTA. KIRKBY T. M. MCCALLA KONRADMENGEL W. H. PATRICK,JR. J . A . SILVA H . T. STALKER G. UEHARA P. W. UNGER P. D. WALTON R. WETSELAAR ADVANCES IN AGRONOMY Prepared in cooperation with the AMERICAN SOCIETY OF AGRONOMY VOLUME 33 Edited by N. C . BRADY International Rice Research Institute Manila, Philippines ADVISORY BOARD H. J . GORZ,CHAIRMAN R.B. GROSSMAN T. M. STARLING I . B. POWELL J . W . BIGGAR M. A. TABATABAI M. STELLY, EX OFFICIO, ASA Headquarters 1980 ACADEMIC PRESS A Subsidiary of Harcourr Brace Jovanovich, Publishers New York London Toronto Sydney San Francisco COPYRIGHT @ 1980, BY ACADEMIC PRESS, INC. ALL RIGHTS RESERVED. NO PART OF THIS PUBLICATION MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM OR BY ANY MEANS, ELECTRONIC OR MECHANICAL, INCLUDING PHOTOCOPY, RECORDING, OR ANY INFORMATION STORAGE AND RETRIEVAL SYSTEM, WITHOUT PERMISSION IN WRITING FROM THE PUBLISHER. ACADEMIC PRESS,INC. I I 1 Fifth Avenue, New York, New York 10003 United Kingdom Edition published by ACADEMIC PRESS, INC. ( L O N D O N ) LTD. 24/ 28 Oval Road, London NWI 7DX LIBRARY OF CONGRESS CATALOG CARD NUMBER:50-5598 ISBN 0-12-000733-9 PRINTED IN THE UNITED STATES OF AMERICA 80 81 82 83 9 8 7 6 5 4 3 2 1 CONTENTS CONTIUBUTORS TO VOLUME 33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PREFACE ..................................................... ix xi CONSERVATION TILLAGE SYSTEMS P. W. Unger and T . M . McCalla I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I1 . Historical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III . Tillage Equipment and Use ............................... IV . Crop Yields and Quality ................................. V . Environmental Consideration ............................. VI . Infiltration and Water Conservation ........................ VII . Weed Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIII . Insects and Plant Diseases ................................ IX . Soil Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X . Soil Structure and Other Physical Properties . . . . . . . . . . . . . . . . . XI . Chemical Effects and Microbial Activity .................... XI1. Economics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XI11. Summary and Conclusions ............................... References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 5 6 13 16 30 35 38 39 43 48 49 51 53 POTASSIUM IN CROP PRODUCTION Konrad Mengel and Ernest A . Kirkby I. I1. 111. IV . V. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Potassium Availability in the Soil .......................... Potassium in Physiology ................................. Potassium Application and Crop Growth .................... Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References ............................................ 59 60 74 91 103 103 UTILIZATION OF WILD SPECIES FOR CROP IMPROVEMENT H . T . Stalker I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I1. Biosystematics ......................................... V 112 113 vi