ADVANCES IN AGRONOMY VOLUME 22 CONTRIBUTORS TO THIS VOLUME K. P. BARLEY J. R. BROWNELL J. w.CARY FRANCISE. CLARK J. P. EVENSON D. L. GRUNES PAUL R. HENSON E. M. HUTTON D. S. MCINTYRE H. F. MAYLAND M. M. MORTLAND ELDORA. PAUL D. L. PLUCKNETT W. G. SANFORD ROBERTR. SEANEY P. R. STOUT ADVANCES IN AGRONOMY Prepared under the Auspices of the AMERICAN SOCIETY OF AGRONOMY VOLUME 22 Edited by N. C. BRADY Roberts Hall, Cornell University, lthaca, New York ADVISORY BOARD W. L. COLVILLE W. A. RANEY I. J . JOHNSON J . R. RUNKLES R. B. MUSGRAVE G. W. THOMAS 1970 ACADEMIC PRESS New York and London COPYRIGHT 0 1970, BY ACADEMIC PRESS,INC. ALL RIGHTS RESERVED. NO PART OF THIS BOOK MAY BE REPRODUCED IN ANY FORM, BY PHOTOSTAT, MICROFILM, RETRIEVAL SYSTEM, OR ANY OTHER MEANS, WITHOUT WRITTEN PERMISSION FROM THE PUBLISHERS. ACADEMIC PRESS, INC. 1 1 1 Fifth Avenue, New York, New York 10003 United Kingdom Edition published by ACADEMIC PRESS, INC. (LONDON) LTD. Berkeley Square House, London W I X 6BA LIBRARYOF CONGRESS CATALOG CARDNUMBER:50-5598 PRINTED IN THE UNITED STATES O F AMERICA CONTENTS CONTRIBUTORS TO VOLUME 22 .................................................................... .................................................................................................... PREFACE ix xi TROPICAL PASTURES E . M. HUTTON 1. Introduction II. 111. IV . V. VI . VII . VII1 . IX . X. XI . XI1 . XI11. XIV . xv . XVI . .................................................................... Climate and Potential for Improved Pastures in the Tropics ................. Role of Plant Introduction ................................................................ Tropical Legumes ... ............................... ................................. Temperate Legumes d in the Subtropics .......................................... Nodulation and Nitrogen Fixation of Tropical Legumes .......................... Legume Nutrition Relative to Tropical Pasture Development ................... Undesirable Compounds in Tropical Legumes ....................................... Physiology of Tropical Legumes .......................................................... Breeding and Genetics of the Main Legumes ......................................... The Main Grasse .................................................... umes ............................................ Phosphorus and Nitrogen Fertilization of Grass Breeding and Genetics of Tropical Grasses Beef Production from Legume-Based Tropi ........................... Summary and Conclusions ........................................... References ........................................................................... CLAY-ORGANIC 2 3 5 8 21 23 27 33 36 39 44 50 53 57 60 65 66 COMPLEXES A N D INTERACTIONS M . M . MORTLAND I. ............................................................................. I 1 . Bonding Mechanisms in Clay-Organic Complexes .................................. I11 . Nature of Some Clay-Organic Complexes and Reactions ........................ IV . Nature and Importance of Some Clay-Organic Complexes in Soils and Sediments ........................................................................................ V . Conclusions ..................................................................................... ................................................................................. V 75 77 95 108 113 I14 vi CONTENTS BIRDSFOOT TREFOIL ROBERTR. SEANEYA N D PAULR. HENSON .................................................... I. I