Nitrogen is the most limiting element for crop production. Traditionally, expensive commercial fertilizers are used to correct soil nitrogen deficiencies. Indeed, 50% of the increase in rice yields after World War II can be attributed to increased fertilizer nitrogen use. Although an increased rate of fertilizer nitrogen application has been advocated to meet the growing demand for food, it is unrealistic to advise the farmers to apply fertilizers they could hardly afford, and whose prices are likely to escalate in the years ahead. In addition, when they are not applied judiciously there are problems of environmental pollution as plants are capable of taking up only a relatively small portion of the applied nitrogen, a substantial amount being lost through various chemical and biological processes. The exploitation of cheaper alternatives or supplements to fertilizers have therefore gained much interest in recent years. Our increased interest in biological nitrogen fixation as a supplement or alternative to nitrogen fertilizers led to the convening of a consultants' meeting on `The Role of Isotopes in Studies on Nitrogen Fixation and Nitrogen Cycling by Blue-Green Algae and the Azolla-Anabaena azollae Association', in Vienna from 11--15 October 1982. The consultants' group recommended that the Joint FAI/IAEA Division of Nuclear Techniques in Food and Agriculture embark on a coordinated research programme in this field and that initial emphasis should be placed on Azolla-Anabaena symbiosis. As a result, such a programme was initiated in 1984, which was concluded in 1989. The results and conclusions reported here are those that were generated during the five years of its operation.

A knowledge of clay is important in many spheres of scientific endeav our, particularly in natural sciences such as geology, mineralogy and soil science, but also in more applied areas like environmental and mater ials science. Over the last two decades research into clay mineralogy has been strongly influenced by the development and application of a num ber of spectroscopic techniques which are now able to yield information about clay materials at a level of detail that previously would have seemed inconceivable. This information relates not only to the precise characterization of the individual clay components themselves, but also to the ways in which these components interact with a whole range of absorbate molecules. At present, however, the fruits of this research are to be found principally in a somewhat widely dispersed form in the scientific journals, and it was thus considered to be an appropriate time to bring together a compilation of these spectroscopic techniques in a way which would make them more accessible to the non-specialist. This is the primary aim of this book. The authors of the various chapters first describe the principles and instrumentation of the individual spectro scopic techniques, assuming a minimum of prior knowledge, and then go on to show how these methods have been usefully applied to clay mineralogy in its broadest context."

The Fifth International Symposium on Nitrogen Fixation with Non-legumes was held in Florence (Italy) on 10-14 September, 1990. Earlier Symposia of this series were held in Piracicaba (Brazil), Banf Alberta (Canada), Helsinki (Finland) and Rio De Janeiro (Brazil). The Symposium's main objectives were to bring together scientists working in many different fields of nitrogen fixation, to stimulate discussion on this important process and to have an appraisal of the most recent studies concerning nitrogen fixation with non-legumes. The Symposium was attended by 230 scientists from 32 different countries. This volume collects the contributions of 65 lectures and 87 posters, which are an up-to-date account of the state of knowledge on biological nitrogen fixation with non-legumes. The book provides a valuable reference source not only for specialists in nitrogen fixation, but also for researchers working on related aspects of agronomy, biochemistry, genetics, microbiology, molecular biology and plant physiology. It is with great pleasure that we aknowledge the contributions of the authors in assuring the prompt pubblication of this volume. We would also like to express our thanks to Kluwer Academic Publishers B.V. for the publication of these Proceedings. M. Polsinelli R. Materassi M. Vincenzini ORGANIZING COMMITTEE President M. Polsinelli M. Vincenzini Secretary F. Favilli Treasurer E. Galli E. Gallori L. Giovannetti R. Materassi M.P. Nuti M.R. Tredici SCIENTIFIC COMMITTEE M. Bazzicalupo Florence, Italy H. Bothe Cologne, West Germany R.H. Burris Madison, U.S.A.

The International Society of Root Research sponsored the Symposium "Root Demographics and Their Efficiencies in Sustainable Agriculture, GrassLands and Forest Ecosystems," July 14-18, 1996, at the Madren Conference Center, Clemson University, Clemson, South Carolina, USA. The conference was a continuation of a series of international symposiums on root research held every three to four years. Symposiums have also been held twice in Vienna, Austria, and once in Uppsala, Sweden, and Almaty, Kazahkstan prior to the meeting at Clemson University. The sponsoring society has made a particular effort in these symposia to include root scientists from the former Soviet Union because of the importance of exchanging information on a worldwide basis. This symposium continued and promoted that effort by providing travel grants to several scientists from that region; however, funds for that purpose were limited. Therefore, in compiling these proceedings, a number of papers from scientists from the former Soviet Union and former Warsaw Pack countries have been included even though the scientists were not actually present for the SymPOSIum.

Sedimentation and Tectonics in Rift Basins: Red Sea - Gulf of Aden presents new case studies and synthesises the results of recent research on the sedimentological evolution of the Red Sea - Gulf of Aden rift system. This rift basin is generally regarded as the best natural geological laboratory in the world in which to study the processes of rift formation. Uplift of the rift margins in an arid climate results in extensive three-dimensional exposures of pre- and syn-rift strata and associated structures. These serve as analogues for the understanding and hydrocarbon exploration of deeper buried rift-systems on continental margins such as the North Sea and the Atlantic margins. The Red Sea - Gulf of Aden rift is also exceptional in that its stratigraphy spans all stages from pre-rift environments, syn-rift continental to marine environments through the rift to drift transition to post-rift sea-floor spreading. The work is arranged in eight sections: following a review of the sedimentology and stratigraphy of rift basins, the magmatism and structural evolution of the Red Sea - Gulf of Aden rift is reviewed. Subsequently, new case studies are presented of the early rifting environment, syn-rift sedimentation, tectonics and diagenesis, evaporites and salt tectonics. Post-rift sediments of the axial trough are then discussed along with studies of reefs, coastal zone and shelf sediments, and the tectonic geomorphology of the rift margin escarpment. This work results from extensive new research in the rift basin largely carried out under collaborative research projects by European and Middle Eastern geologists. It will be an invaluable reference work for geoscientists in the hydrocarbon, groundwater and mineral extraction industries, as well as for researchers in university departments of earth sciences, mining and physical geography.

The first edition of Practical Sedimentology contained dis ACKNOWLEDGMENTS cussions of principles and techniques that could be applied to the analysis of sediments in the field and in laboratories sup Colleagues at the University of Canterbury and the Univer plied with inexpensive and commonly available equipment. sity of New England, Lismore, have helped with practical When considering a revised edition, we felt that it was inap advice on their experiences with various methodologies dis propriate to restrict consideration to the simple and common cussed in this volume. At the University of Canterbury, we techniques because so many modern analyses of sediments are particularly grateful to K. Swanson for advice on prepar use sophisticated and often expensive equipment to examine ing materials for scanning electron microscopy and paleonto sediments and sedimentary rocks. A review of the wide range logical specimens; to G. Coates (working at the university at of available techniques and equipment was not feasible in the the time of the first edition of Practical Sedimentology) for same volume as a review of principles. The original intent to compilation of, and additions to, the procedures for textural analysis and some tables and sketches; to Ted Montague for produce a concise summary of practical sediment studies in an inexpensive format was maintained, but now in the form the bulk of the chapter on borehole sedimentology; to Dr. J.

Selenium is a naturally occurring trace element that can become concentrated and released by industrial, agricultural, petrochemical and mining activities. At concentrated levels it is toxic and has polluted ecosystems around the world. This book will serve as a comprehensive practical handbook for everyone dealing with selenium in aquatic environments. It offers field-tested approaches and methods for assessment and water quality management. Using his twenty-year experience, the author discusses the effects of selenium on fish and bird populations and presents guidelines for identifying sources of pollution, interpreting selenium concentrations, assessing hazardous conditions, setting water quality criteria and ecosystem loading limits (TMDLs). He also includes a procedure for setting environmentally safe limits that ensure compliance with EPA regulations. Selenium Assessment in Aquatic Ecosystems will interest field scientists, natural resource managers, risk assessors and environmental planners.

The majority of this book was written in 1983-84 while the senior author was a Visiting Scientist at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee. We believe that the approach to the problem of acid deposition effects on soils and waters developed during this collaboration contains ele ments that are significantly different from most prior work in this area. Some of the material and the software used in the development of these concepts stem from earlier individual efforts of the authors. However, what we believe to be the more significant concepts concerning the processes by which alkalinity may be developed in acid soil solutions, and by which acid deposition may contrib ute to the loss of this alkalinity, were the result of this collaboration. The ultimate usefulness of these concepts in understanding and dealing with various aspects of the problems associated with acid deposition cannot be adequately gauged at the present time. They must first withstand tests of con sistency with available observation, and of direct experimentation. It is our hope that dissemination through this book will facilitate this process within the scientific community. The authors wish to thank the administration of the Environmental Science Division at ORNL, and the College of Agricultural Sciences at Colorado State University for their support in arranging this collaboration. We also wish to express our appreciation for the financial support provided by EPA. Personal thanks are due to Dr."

The increasing global demand for food and other agricultural products calls for urgent measures to increase water use efficiency which is, with plant nutrient availability, one of the two main limiting factors in crop production. Although only 20% of all cultivated land in the world is under irrigation, it provides 35-40% of all crop production. Because of higher yields under irrigated agriculture, investments for irrigation are usually a top priority. However, it has become a matter of serious concern in recent years that, despite their high co~ts, the performance of many irrigation projects has fallen short of expectations as a result of inadequate water management at both farm and system levels. Crop production increase has been well below the project targets. The greatest potential for increasing food and other agricultural products is the more efficient use of naturally occurring precipitation in conjunction with improved soil fertility management. Until recently, regardless of the amounts and distribution of rainfall, irrigation practices were used almost exclusively to supplement the amount of soil water stored in the root zone to such an extent that the available soil water never allowed the crop to suffer from water stress throughout the growing season. As a result, even today farmers still tend to over-irrigate to ensure a bountiful amount of water stored.

In this study, an overview is presented of agricultural policies on manure and minerals, relating to the Nitrate Directive to remedy excessive surface- and groundwater contamination from intensive agricultural practices. Six countries belonging to the European Union were studied: the Netherlands, Belgium, Denmark, France, Germany and the United Kingdom. The policies and their legal incorporation were related to agricultural and environmental conditions in each country. In addition, an inventory was made of agricultural mineral poli cies in the United States and Canada. Conditions for livestock farming in North America differ considerably from those in Europe, but their solutions shed a different light on European policies. Research has shown that there are still very considerable mineral surpluses in many countries and regions. In both the Netherlands and in the Flemish part of Belgium, existing problems due to very high levels of manure production are structural rather than local and cannot easily be solved by transport of manure to other regions. To a lesser extent. Germany, Denmark and relatively small parts of France (Brittany) and the United Kingdom, still exceed the norms for an equilibrium fertilization. In Denmark, existing problems can probably be solved within the existing legislative framework. The Netherlands, Flanders. several German Lander (Nordrhein-Westfalen and Schleswig-Holstein) and Brittany.

Bioremediation - the use of microorganisms for environmental clean-up - is a technology that is experiencing a rapid phase of development. From the opening chapter of Perspectives in Bioremediation, on the nature of environmental site assessment, on to the genetic manipulation of native soil microorganisms, the international collection of authors provide an understanding of the current progress and limitations of technologies that are designed to help nature herself. The book draws together many different aspects of environmental remediation: the environmental engineer is introduced to the bacteria of contaminated environments and the ideas developing from genetic engineering; the environmental microbiologist can grasp site assessment and the predictive kinetic analysis of potentials. The book provides a clear and concise introduction to the nature of and potential for bioremediation to contribute to a critical global effort in eliminating contamination of the world's resources and to start to reverse decades of environmental mismanagement and neglect.

In the Netherlands the Institute for Soil Fertility Research plays a major role in soil biological, soil physical and plant nutritional research on the availability of nitrogen to crops. Main subjects of research are nitrogen turnover in the crop-soil ecosystem through biological transformations, nitrogen transport through the soil and nitrogen losses by leaching, denitrification and volatilization, and nitrogen use efficiency of various crops and cropping systems. The current knowledge in the different fields of research is integrated in simulation models. Simulation models not only make it possible to summarize and structure knowledge, but also, after verification, to extra- late the knowledge to situations different from the situations that have actually been studied. Such research is also carried out in other European and non-European countries. To compare the various simulation models currently in use, a workshop was organized by the Institute for Soil Fertility Research on 5-6 June 1990 on the occasion of its centennial. The title of the workshop was 'Nitrogen turnover in the soil-crop:: cosystem: modelling of biological transformations, transport of nitrogen and nitrogen use efficiency'. The 40 Jarticipants, who came from Canada and various European countries, were requested to run their model with data Jrovided by the Institute prior to the workshop. Data from 18 cases were made available to the participants: three ocations, three treatments, and two seasons.

A review of such natural disasters as floods and landslides, highlighting the possibility of safe and correct land planning and management by means of a global approach to territory. Since the events deriving from slope and fluvial dynamics are commonly triggered by the same factor, occur at the same time and are closely related, this book analyses floods and slope stability phenomena as different aspects of the same dynamic system: the drainage basin.

Here is a collection of papers from BIOGEOMON, The Fourth International Symposium on Ecosystem Behavior. The contributions address a wider-than-ever range of concerns: aspects of catchment monitoring and modeling; nitrogen transformations and processes; stable and radiogenic isotopes; biogeochemistry of restored ecosystems; and the dynamics of such chemicals as mercury and phosphorous, among many other topics.

Collapsing engineering soils are a formidable hazard around the world. These difficult materials also include some of the world's most fertile agricultural soils, fostering dense human populations which are therefore increasingly at risk. Despite an impressive literature on the engineering aspects of collapsing soils, these materials are coming under increasing scrutiny by scientists in other fields. This is most evidently the case with soil scientists, stratigraphers and sedimentologists. Past earth surface conditions have a direct influence on the detailed behaviour of collapsible soils: as a complement, these materials also provide detailed data on changing global climates. The selected papers presented here highlight the common ground between three scientific groups with a vested interest in a better understanding of collapsible soils.

This manuscript was made possible by the exceptional support provided by INSA (Institut National des Sciences Appliquees) Toulouse, the University of New Mexico and the University of Cincinnati College of Engineering. The authors, as listed in this book, took the time to prepare excellent manuscripts focusing on scientific and technical areas relevant to emerging environmental issues. These manuscripts were rigorously reviewed and refereed by scientists and engineers before inclusion in this book. An introductory chapter was prepared to summarize and integrate technical issues covered and the last chapter was written to present policy perspectives. The editors are most grateful to the contributors, sponsor organizations, and many colleagues who were kind enough to assist us in making this manuscript possible. Background information about the editors, principal authors and other contributor: s to this manuscript follows. Editors Professor Dr. Ravi K. Jain Associate Dean for Research and International Engineering College of Engineering University of Cincinnati Mail Location 0018 Cincinnati OH 45221-0018 U.S.A

all such systems are important, the Proterozoic column This volume concerns the geology of China, and it examinesthat concern by expositionsofthe stratigraphy, possibly is unique in its continuous sedimentary devel the paleogeography, and the tectonics ofthat remarkable opment and in its reference section of global rank. In paleogeography, this volume describes and illustra country. In this sense, therefore, our aims and purposes are explicit in the title. The senior author and his tes first the broad distribution of Proterozoic deposits. colleagues, furthermore, do not have in mind any special Succeeding descriptions and illustrations trace the ebb and flow of shallow marine waters across China as or specific audience. This volume is quite simply for all geologists. By far the majority will be those whose Phanerozoic time of more than 600 million years elapses native tongue is English, or those who understand from the beginning of the Cambrian to the present. In structure, this volume emphasizes the importance English. Not to be overlooked, moreover, is the large number ofChinese geologists who not only read English of paraplatforms, platforms, geosynclines, and great but also who themselves write studies in English that east-west zones of fracture in the Precambian, also the appear in publications in both their homeland and effects of these early structural elements on structure abroad. in the ensuing Phanerozoic. In the Phanerozoic itself, north-south stress developed in the pre-Phanerozoic A constantly growing interest in the geology of China continued through much of the Paleozoic."

The NATO Advanced Research Workshop on "Paleoclimatology and Paleometeorology: Modem and Past Patterns of Global Atmospheric Transport" (held at Oracle, Arizona, USA from November 17-19, 1987) brought together atmospheric chemists, physicists, and meteorologists who study the origin and transport of modem-day mineral and biological aerosols with geologists and paleobotanists who study the sedimentary record of eolian and hydrologic processes along with modelers who study and conceptualize the processes influencing atmospheric transport at present and in the past. Presentations at the workshop provided a guide to our present knowledge of the entire spectrum of processes and phenomena important to the generation, transport, and deposition of eolian terrigenous material that ultimately becomes part of the geologic record and the modeling techniques that used to represent these processes. The presenta tions on the geologic record of eolian deposition documented our present understanding of the na~e and causes of climate change on time scales of the last glacial ages (tens of thousands of years) to time scales over which the arrangement of continents, mountains, and oceans has changed sub stantially (tens of millions of years). There has been a growing recognition of the importance of global climatic changes to the future well-being of humanity. In particular, the climatic response to human alterations to the earth's surface and chemical composition has led to concern over the agricultural, ecological, and societal impacts of such potential global changes.

The Guayana Highlands in northeastern tropical America, rising from lowland rain forests and savannas up to 3000 m elevation, are characterized by ancient tablelands called "tepuis." The peatlands that developed on the tepuis constitute unique and fascinating ecosystems and are the focus of this volume, which starts with an overview of tropical and subtropical peats, followed by an introduction to the geo-ecological features of the Guayana region as a whole, with special emphasis on the diversity of the vegetation cover from lowlands to uplands to highlands. The core subject centers on the properties and dating of the peat deposits and the interpretation of the chronological record in terms of past environmental changes. The well illustrated book will appeal to a broad range of scientists interested in tropical highland peats, including quaternarists, soil scientists, geomorphologists, geographers, geologists, ecologists, botanists, hydrologists, conservationists, and land use planners.

This volume, although not an integrated synthesis, treats most aspects of Holocene sedimenta tion and diagenesis in the Persian Gulf, grouping 22 contributions under a single cover and in one language. Because these sediments and diagenetic minerals are comparable to those existing in many ancient sedimentary basins, their appraisal should be of value to the enlarging group of workers who interpret ancient sedimentary rocks. The essential morphological, climatic and oceanographic factors determining Holocene sedimen tation and diagenesis in the Persian Gulf are summarized in the introductory article by PURSER and SEIBOLD. These environmental controls and the overall morphology of the Persian Gulf have much in common with Shark Bay, Western Australia, described by LOGAN et al. (1970). On the other hand, the Persian Gulf is markedly different from the better known Florida and Bahamian prov inces; the floor of the Persian Gulf is gently inclined from continental shoreline to bathymetric axis (80-100 m); the Bahamian province, on the other hand, is horizontal and extremely shallow (2-10 m), with very sharply defined shelf edges surrounded by deep oceanic waters. These contrast ing architectural styles are related to different tectonic frames.

"Soil Health and Climate Change" presents a comprehensive overview of the concept of soil health, including the significance of key soil attributes and management of soil health in conventional and emerging land use systems in the context of climate change. Starting with a review of the physical, chemical and biological indicators of soil health and their significance for monitoring the impacts of climate change, this book then focuses on describing the role of soil structure, pH, organic matter, nitrogen, respiration and biota in sustaining the basic functions of soil ecosystems, and their anticipated responses to climate change. Further topics include the management of cropping, pastoral, and forestry systems, and rehabilitated mine sites, with a focus on mitigation of and adaptation to climate change impacts. Finally, the opportunities and potential risks of organic farming, biochar and bioenergy systems, and their ability to sustain and even enhance soil health, are discussed.

Environmental Chemistry is a relatively young science. Interest in this subject, however, is growing very rapidly and, although no agreement has been reached as yet about the exact content and limits of this interdisciplinary subject, there appears to be increasing interest in seeing environmental topics which are based on chemistry embodied in this subject. One of the first objectives of Environ mental Chemistry must be the study of the environment and of natural chemical processes which occur in the environment. A major purpose of this series on Environmental Chemistry, therefore, is to present a reasonably uniform view of various aspects of the chemistry of the environment and chemical reactions occuring in the environment. The industrial activities of man have given a new dimension to Environ mental Chemistry. We have now synthesized and described over five million chemical compounds and chemical industry produces about one hundred and fifty million tons of synthetic chemicals annually. We ship billions of tons of oil per year and through mining operations and other geophysical modifications, large quantities of inorganic and organic materials are released from their natural deposits. Cities and metropolitan areas of up to 15 million inhabitants produce large quantities ofwaste in relatively small and confined areas. Much of the chemical products and was te products of modern society are released into the environment either during production, storage, transport, use or ultimate disposal. These released materials participate in natural cycles and reactions and frequently lead to interference and disturbance of natural systems."

Avalonian and Cadomian Geology of the North Atlantic aims to provide region by region syntheses of those terranes which are believed to have once formed part of the Late Proterozoic Avalonian-Cadomian belt. The belt originally comprised a series of volcanic arcs and marginal basins formed during the period c. 700-500 Ma ago, producing a range of calc-alkaline volcanics and intrusives and marginal basin sediments partly founded on continental basement rocks. Originally about 9000 km long, the belt is made up of a number of terranes later separated by the Caledonian orogeny (c. 500- 400 Ma), Variscan orogeny (c. 325 Ma), and the recent opening ofthe Atlantic Ocean (c. 70 Ma). The rocks therefore are now located on both sides of the Atlantic, as far apart as Florida and Czechoslovakia. A possible modern analogue for the Avalonian-Cadomian belt may be the present-day Western Pacific margins. We believe that a synthesis such as this provides the basis for correlation of the timing of events and hence improves our understanding of the underlying tectonic framework of the belt. This book developed from the recognition of, first, our own lack of knowledge of contemporaneous events outwith Armorica, and, second, the likelihood that other researchers working on individual areas or terranes do so in relative isolation. We have therefore commissioned chapters from researchers considered to be experts on their own particular areas.

Marine Clastic reservoirs provides an integrated perspective to sandstone reservoir description and analysis. It combines analog-oriented methods fromsequence stratigraphy with rigorous stratigraphic and sedimentological description of cores and outcrops to develop a process-based analysis of sandstone facies. Twelve chapters, divided into 3 sections, first describe the specific use of sequence stratigraphy to catalog, identify, andpredict marine clastic reservoir facies. Next they examine the importance ofrigorous sedimentological and geomorphic description. Finally, marine depositional environments from delta systems to deep-sea fans arereviewed to give examples of these improved descriptive and analytical techniques

Soils form a unique and irreplaceable essential resource for all terrestrial organisms, including man. Soils form not only the very thin outer skin of the earth's crust that is exploited by plant roots for anchorage and supply of water and nutrients. Soils are complex natural bodies formed under the influence of plants, microorganisms and soil animals, water and air from their parent material, i.e. solid rock or unconsolidated sediments. Physically, chemically and mineralogically they usually differ strongly from the parent material, and normally are far more suitable as a rooting medium for plants. In addition to serving as a substrate for plant growth, including crops and pasture, soils play a dominant role in the biogeochemical cycling of water, carbon, nitrogen and other elements, influencing the chemical composition and turnover rates of substances in the atmosphere and the hydrosphere. Soils take decades to millennia to form. We tread on them and do not usually see their interior, so we tend to take them for granted. But improper and abusive agricultural management, careless land- clearing and reclamation, man-induced erosion, salinisation and acidification, desertification, air- and water pollution, and withdrawal of land for housing, industry and transportation now destroy soils more rapidly than they can be formed.