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NITRATE, AGRICULTURE AND THE ENVIRONMENT This book is dedicated to the memory of Sir John Bennet Lawes Scientist Entrepreneur Man of Principle His memorial in Harpenden Parish Church reads: In affectionate memory of Sir John Bennet Lawes Baronet FRS only son of the above John Bennet Lawes born at Rothamsted Dec. 28th 1814 died at Rothamsted Aug. 31 1900. His long life and his great knowledge were to the last devoted to far-reaching investigations into all scientific matters which could affect agriculture. The results obtained were freely given for the ben- efit of his fellow men both in his own country and in all parts of the world. This tablet is erected by Parishioners of Harpenden and others who deeply feel his loss as an example and a friend. Sir John Bennet Lawes, LLD, FRS, FCS. (Photograph courtesy of Rothamsted Research.) NITRATE, AGRICULTURE AND THE ENVIRONMENT T.M. Addiscott Lawes Trust Senior Fellow Rothamsted Research, Harpenden, UK CABI Publishing CABI Publishing is a division of CAB International CABI Publishing CABI Publishing CAB International 875 Massachusetts Avenue Wallingford 7th Floor Oxfordshire OX10 8DE Cambridge, MA 02139 UK USA Tel: +44 (0)1491 832111 Tel: +1 617 395 4056 Fax: +44 (0)1491 833508 Fax: +1 617 354 6875 E-mail: [email protected] E-mail: [email protected] Website: www.cabi-publishing.org ©T.M. Addiscott 2005. All rights reserved. No part of this publication may be reproduced in any form or by any means, electronically, mechanically, by photocopying, recording or otherwise, without the prior permission of the copyright owners. A catalogue record for this book is available from the British Library, London, UK. Library of Congress Cataloging-in-Publication Data Addiscott, T. M. (Tom M.) Nitrate, agriculture and the environment / by T.M. Addiscott p. cm. ISBN 0-85199-913-1 (alk. paper) 1. Nitrogen fertilizers. 2. Nitrogen fertilizers--Environmental aspects. I. Title. S651.A3199 2004 631.8´4--dc22 2004017344 ISBN 0 85199 913 1 Typeset by MRM Graphics Ltd, Winslow, Bucks Printed and bound in the UK by Biddles Ltd, King’s Lynn Contents Contributors vii Preface ix 1 Dependence on Nitrogen 1 2 The Chemistry and Physics of Nitrate 14 3 The Biology of Nitrate 29 4 Nitrogen Fertilizer 48 5 Losses of Nitrogen from Arable Land 62 6 Losses of Nitrogen from Grassland 93 7 Nitrate in Fresh Water and Nitrous Oxide in the Atmosphere 110 With a contribution from Arthur J. Gold and Candace A. Oviatt 8 Nitrate in Coastal Waters 127 Contributed by Candace A. Oviatt and Arthur J. Gold 9 Nitrate and Health 145 Based on material contributed by Nigel Benjamin 10 The Politics and Economics of Nitrate 153 11 Nitrate in Africa: The ‘Western Hegemony’ 172 With a contribution from Ken Giller 12 Risk 185 13 Coming to Terms with Nitrate: Public Attitudes to Science 204 v vi Contents 14 Coming to Terms with Nitrate: Land Use 225 References 252 Index 269 Contributors Tom Addiscott had worked at Rothamsted for 36 years when he retired in 2002. He keeps in contact with the institute as a Lawes Trust Senior Fellow associated with the Agriculture and Environment Division and remains involved in the organization of the ‘Manor Recitals’ – concerts at Rothamsted Manor. Much of his research at Rothamsted concerned the development and use of simple computer models for the leaching of nitrate and phosphate and associated processes such as mineralization, crop growth and nutrient uptake. He also worked on model validation (evaluation) and the problems that arise from the interaction between (statistical) error in parameters and non-linearity in models. One of his retirement projects is to apply Complexity Theory in a soils context. He has been writing on the ‘nitrate problem’ for nearly 20 years, and a pre- vious book, Farming, Fertilizers and the Nitrate Problem, written with Andy Whitmore and David Powlson, was published by CAB International in 1991. On leaving Oxford in 1964, Tom Addiscott spent a year as a UNA International Service volunteer working on soil phosphate in Tanzania. He then worked for just over a year for the Lawes Chemical Company before moving to Rothamsted in 1966. He retains an interest in Africa and is a member of the FARM-Africa charity, with whom he has trav- elled in recent years to Kenya, Tanzania and Ethiopia. He was licensed as a Reader in the Church of England in 1978. Tom Addiscott claims the distinction of being one of the very few, possibly only two, people to have worked at both of the institutions founded by Sir John Bennet Lawes, the Lawes Chemical Company and Rothamsted Experimental Station. He was also presented with the Gold Medal of the Royal Agricultural Society of England in 1991, appointed a Visiting Professor at the University of East London in 1997 and awarded a DSc degree by Oxford University in 1999. vii viii Contributors Art Gold is a Professor in the Department of Natural Resource Sciences, College of the Environment and Life Sciences, in the University of Rhode Island, Kingston, Rhode Island, USA. Candace Oviatt is Professor of Oceanography at the Graduate School of Oceanography in the University of Rhode Island, Narragansett, Rhode Island, USA. Nigel Benjamin was until recently Head of the William Harvey Research Institute, Queen Mary College, London and has moved to join the Peninsula Medical School. Ken Giller is Professor of Plant Production Systems in the Department of Plant Sciences at Wageningen Agricultural University, The Netherlands. He was until recently Professor of Soil Science at the University of Zimbabwe, Harare. Preface Another book about nitrate? The most important incentive for this new book lies in the realization by Vaclav Smil and David Jenkinson that the world is collectively in a state of dependence on the production of nitrogen by the Haber–Bosch process. We may not like the fact but, because of pop- ulation growth, we can no more give up nitrogen fertilizer than an addict can give up heroin, less so in fact. The production and use of nitrogen fer- tilizer inevitably lead to losses of nitrate and nitrous oxide to the environ- ment and we have to learn to deal with them. There can be no return to a state of ‘innocence’. The preface to the earlier book that Andy Whitmore, David Powlson and I wrote about nitrate, Farming, Fertilizers and the Nitrate Problem (Addiscott et al., 1991), said that book was in response to fears that nitrate from agriculture had found its way into drinking water, causing stomach cancer in adults and cyanosis in infants, and into rivers and seas, where it was causing the growth of toxic algae and general mayhem in otherwise balanced natural ecosystems. There were also fears of a ‘nitrate time bomb’ moving inexorably towards our taps. Those fears have not entirely abated and still appear regularly in the press and even scientific papers from time to time. But much has changed in our knowledge about nitrate during the past 13 years, and the new understandings have not received the publicity they deserve. I hope, if you read this book, you will see why it was needed. The most startling change in our understanding is the realization that, rather that being a threat to our health, nitrate plays a central role in our bodies’ defence system against bacterial gastroenteritis. This may explain why our bodies go to considerable efforts to maintain their supply of nitrate against the attempts by various official bodies to stop them doing so. The limits on nitrate in drinking water were, in the words of J.-L. L’hirondel, ‘a world-scale scientific error that has lasted more than 50 years’. These limits can be seen, on re-examining early papers on well-water methaemoglobi- ix x Preface naemia, to be the results of the unfortunate juxtaposition of wells and pit privies. Nigel Benjamin played a leading role in the research on the positive role of nitrate in health, and I am grateful to him for supplying most of the information in Chapter 9 and some of that in Chapter 10. The understanding of the effects of plant nutrients in the environment has also increased during the past 13 years. It is now clear that phosphate rather than nitrate is the limiting factor for algal blooms in fresh water, but that nitrate is responsible for blooms and other problems in estuarine and marine coastal waters. Art Gold and Candace Oviatt kindly contributed the whole of Chapter 8, which deals with nitrate effects in marine waters, and also some of the material on fresh water in Chapter 7. Another topic on which understanding has increased is nitrous oxide. We know more about its generation in the soil, particularly in agricultural operations, and its less than desirable effects in the atmosphere, particularly the stratosphere. Assessing emissions of this gas is a considerable challenge because of the scale issue involved. Nitrous oxide is a global pollutant and is discussed at various scales in parts of Chapters 3, 5, 6 and 7. Losses of nitrate and nitrous oxide from grassland are much more diffi- cult to research than those from arable land. Cows are a formidable compli- cation, but a lot of interesting progress has been made on grassland in the last decade. Losses of both pollutants from both types of systems are dis- cussed in Chapters 5 and 6, respectively. The book covers, in Chapters 1, 2 and 3, the basic soil chemistry, physics and biology discussed in the previous book, and I am grateful to Andy Whitmore and David Powlson for agreeing to my using material from the previous book as well as new material.

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