ADVANCES IN AGRONOMY VOLUME 40 This Page Intentionally Left Blank ADVANCES IN AGRONOMY Prepared in Cooperation with the AMERICAN SOCIETY OF AGRONOMY VOLUME 40 Edited by N. C . BRADY Science and Technology Agencyfor International Development Department of State Washington,D.C. ADVISORY BOARD H. J. GORZ,CHAIRMAN M. A. TABATABAIT. M. STARLING E. J. KAMPRATH R. J. KOHEL G. E. HAM G. H. HEICHEL E. L. KLEPPER R. A. BRICCS,Ex OFFICIO ASA Headquarters 1986 ACADEMIC PRESS, INC. Harcourt Brace Jovanovich, Publishers Orlando San Diego New York Austin Boston London Sydney Tokyo Toronto COPYRIGHT @ 1986 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 Orlando. Florida 32887 United Kingdom Edition published b y ACADEMIC PRESS INC. (LONDON) LTD. 24-28 Oval Road. London NWI 7DX LIBRARY OF CONGRESS CATALOG C A R D N U M B E R : 50-5598 ISBN 0-12-000740-1 (alk. paper) PRINTED IN THE UNITED STATES OF AMkRlCA 86878889 9 8 1 6 5 4 3 2 1 CONTENTS PREFACE............................................ vii AGRONOMY OF WHITE CLOVER J . Frame and P. Newbould I. Introduction .......................................... I1. Morphology and Function............................... Environment ......................................... Culture .............................................. Nitrogen Fixation., .................................... Quality .............................................. Grass/White Clover Dynamics ........................... Production and Management ............................ Potential Production ................................... X . Management Guidelines ................................ XI . Conclusions .......................................... References............................................ 111. IV. V. VI. VII. VIII . IX. 1 4 10 20 38 41 45 49 67 69 70 75 AGRONOMIC VALUE OF UNACIDUIATED AND PARTIALLY ACIDULATED PHOSPHATE ROCKS INDIGENOUSTO THE TROPICS L. L. Hammond. S. H . Chien. and A . U . Mokwunye I . Introduction .......................................... I1. Indigenous Phosphate Deposits in the Tropics............... I11. Agronomic Potential of Phosphate Rock for Direct Application .................................. IV . Physical Factors Influencing Expression of Agronomic Potential ................................. V. Soil Factors Influencing Expression of Agronomic Potential . . . VI . Climatic Factors Influencing Expression of Agronomic Potential ................................. VII. Partial Acidulation of Phosphate Rock ..................... VIII. Regional Findings on Direct Application of PR and PAPR .... IX . Summary and Conclusions .............................. References............................................ V 89 90 93 101 104 110 112 116 134 137 vi CONTENTS CROP SIMULATION MODELS IN AGRONOMIC SYSTEMS F. D. Whisler, B. Acock, D. N. Baker, R.E. Fye, H. F. Hodges, J. R. Lambert, H. E, Lemmon, J. M. McKinion, and V. R. Reddy I. Need for Crop Simulation Models and Types of Models. ...... 11. Model Building. ....................................... 111. Model Testing ........................................ IV. Model Applications .................................... V. Summary.. .......................................... References. ........................................... 141 146 175 180 204 204 UREA