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Grasslands around the world provide most of the world's milk and wool and much of the meat. The growing world population and global warming have put increased pressure on the world's grasslands. Ross Humphreys has played a leading role in the development of grassland science and in this authoritative review discusses how it has evolved over the past sixty years. Using the proceedings of the International Grassland Congress since 1937, Humphreys identifies the shifting emphasis of the science, assesses the current situation and provides perspectives for its future direction.
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Grasslands around the world provide most of the world's milk and wool and much of the meat. The growing world population and the threat of global warming have put increased pressure on the world's grasslands. Ross Humphreys has played a leading role in the development of grassland science and in this authoritative review discusses how it has evolved over the past 60 years. Using the proceedings of the International Grassland Congress since 1937, Professor Humphreys identifies the shifting emphasis of the science, assesses the current state of play and looks at perspectives for the future. This unique review will be of great value to all grassland scientists and ecologists. THE EVOLVING SCIENCE OF GRASSLAND IMPROVEMENT THE EVOLVING SCIENCE OF GRASSLAND IMPROVEMENT L.R. HUMPHREYS Emeritus Professor of Agriculture, University of Queensland, St Lucia, Australia CAMBRIDGE UNIVERSITY PRESS CAMBRIDGE UNIVERSITY PRESS Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sao Paulo Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9780521495677 © Cambridge University Press 1997 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 1997 This digitally printed version 2007 A catalogue record for this publication is available from the British Library Library of Congress Cataloguing in Publication data Humphreys, L. R. The evolving science of grassland improvement / L. R. Humphreys. p. cm. Includes bibliographical references (p. ) and index. ISBN 0 521 49567 9 1. Pastures. 2. Forage plants. 3. Grasslands. 4. Pasture ecology. 5. Grassland ecology. I. Title. SB199.H84 1997 633.2'02-dc20 96-9419 CIP ISBN 978-0-521-49567-7 hardback ISBN 978-0-521-03873-7 paperback To I.L.H. Contents Preface A cknowledgemen ts Abbreviations 1 2 page xiii x vi xvii Grassland improvement and environmental protection 1.1 The science of grassland improvement 1.2 Functions and properties of pasture systems 1.2.1 Production from grasslands 1.2.2 Production from forages in integrated cropping systems 1.2.3 Social utility of grasslands 1.2.4 Properties of grassland systems 1.3 Atmospheric pollution and global warming 1.3.1 The global warming scenario 1.3.2 Carbon flux and grasslands 1.3.3 Grassland response to CO2 enrichment 1.3.4 Grassland response to changes of temperature, humidity and rainfall 1.3.5 Management options 1.4 Conclusion 1 1 3 3 19 21 26 The plant genetic base for grassland improvement 2.1 Introduction 2.2 Criteria of merit in forage plants 2.2.1 Forage quality 2.2.2 Plant growth 2.2.3 Ecological success in the farm situation 2.3 Conservation of germplasm and plant introduction 29 29 30 30 35 42 50 3 4 6 8 9 11 17 IX Contents 2.3.1 The rationale for conservation of germplasm 2.3.2 The development of collections 2.3.3 Imperatives for plant introdu