Some major developments in soil science since the mid-1960s

Geoderma 100 Ž2001. 403–426 www.elsevier.nlrlocatergeoderma

Some major developments in soil science since the mid-1960s A.R. Mermut a,) , H. Eswaran b a

Department of Soil Science, Saskatchewan Center for Soil Research, UniÕersity of Saskatchewan, 51 Campus DriÕe, Saskatoon, SK, Canada S7N 5A8 b USDA Natural Resource ConserÕation SerÕice, P.O. Box 2890, Washington, DC 20013, USA Received 29 January 2001; received in revised form 1 March 2001; accepted 1 March 2001

Abstract Although the science of soil was established about 150 years ago with the modern soil science taking off after the Second World War, the new Millennium has brought other challenges and new opportunities. Rapidly increasing population in countries that can least afford it have made them food-insecure. With inadequate inputs in agriculture, developing countries are degrading their lands rapidly and destroying ecosystems. Affluence in the richer countries has precipitated other problems hampering ecosystem functions and quality of land resources. These changing conditions have placed new demands on both the society and the soil science community. The latter has resulted in new areas of soil sub-disciplines such as land and soil quality, land degradation and desertification, cycling of bio-geochemicals, soil pollution assessment and monitoring etc. Advances in information technology have also enabled the science to meet the new demands of the enviro-centric world. In the last decade, noticeable changes are evident in methods and research priorities in the discipline. Soil resource assessment and monitoring is entering a new era, in terms of quality of information produced by new information technologies through the innovative use of Geographic Information Systems and remote sensing and significantly improving the acceptance and use of soil survey information. Electronic technology has dramatically increased the demand for and ability to process more data. Other innovations have resulted in quantitative approaches in soil genetic studies and demonstrated the integral role of soils in ecosystems. For global and regional resource assessment, concepts and procedures were refined. The World Reference Base for soil classification and the Global Soil and Terrain Database are the first steps towards standardisation and a more detailed assessment of global soils. The global assessment of human-induced land degradation and vulnerability to desertification are benchmark products of the databases. Environmental pollution and its effects on human and ecosystem health have become public concerns and soil science has contributed to localising, quantifying, and developing mitigation technologies to address the problems. The challenges of climate change and the charge

)

Corresponding author. Fax: q1-306-966-6881. E-mail address: [email protected] ŽA.R. Mermut..

0016-7061r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 1 6 - 7 0 6 1 Ž 0 1 . 0 0 0 3 0 - 1

404

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

to maintain ecological integrity have been met with technologies such as conservation tillage, agroforestry, precision agriculture etc. New concepts such as multi-functionality of land, soil quality, sustainability of agriculture and carbon sequestration, have emerged leading to new management strategies and an enhanced quality of life. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Carbon cycles; Land degradation; Soil quality; Soil information system; Pedometrics; Soil technologies; Agroforestry; Conservation tillage; Micromorphology; Environmental pollution; Societal affairs; World Reference Base

1. Introduction Soil science, since its inception some 150 years ago, has made significant contributions to the quality of human life and has enhanced our understanding of soil resource management to meet the food and fibre needs of humans. In the last few decades, it has become clearer that this task has to be done in the context of a functional ecosystem. The ability to feed the burgeoning population currently at 6.2 billion people, while enabling the multi-functionality of land, has raised concerns on food security. The consequence is a new challenge that seeks a balance between human demands and ecosystem services and their integrity. This changing demand of society has spurred new areas of investigation such as soil quality in relation to water quality, land degradation, cycling of bio-geochemicals, etc. There is an ongoing debate on the role of science in society and societal responsibility to support science ŽLubchenco, 1998. and such discussions are leading to paradigm shifts in institutions responsible for soils and the investigations being undertaken by soil scientists. The study of soils as a science and the need for information on the resource base has been questioned as evidenced by changes in university curricula and the downsizing of soil institutions. Thus, although modern soil science saw its birth after the Second World War, it is faced with new challenges at the beginning of the new millennium, challenges that question even its relevance and need. Part of this dilemma has resulted from the fact that soil science did not establish its role in environmental studies, until recently. Since the 1980s, a dramatic change has taken place in our thinking about utilisation of natural resources. There has been an increased awareness of ecosystem health and maintaining the quality of the environment, and rate of resource consumption, even in the Third World countries. The concept of sustainable development initiated by the Bruntland Commission Ž World Commission on Environment and Development, 1987. , which is amplified by Agenda 21 of the United Nations Conference for Environment and Development ŽUnited Nations Conference on Environment and Development, 1992. , has been the driving force in our research and development.

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

405

In the last decade, noticeable changes are evident in methods and research priorities in the discipline. While soil survey in its traditional role is diminishing, the need for soil information is becoming more important in terms of sustainable land management, ecosystem health, and cycling of biogeochemicals. Soil resource assessment and monitoring is entering a new era, in terms of quality of information produced by new information technologies through the innovative use of Geographic Information Systems Ž GIS. and remote sensing. Despite the fact that many concepts, methodologies, and information have been taken from earth sciences, such as sedimentary petrology, hydrology, geomorphology, and mineralogy, soil science evolved as a discipline of its own, specifically to serve agricultural purposes. The need for soil information to support agriculture resulted in the teaching of soils as an integral part of the agricultural curriculum. Soil research was directed to support the efforts to enhance crop productivity until about the last decade. A major factor that is forging a better alliance is the impetus provided by global climate change studies that requires a better understanding and quantification of earth’s surface processes. Although the need to ensure productivity of the soil has not diminished, the additional investigations to support global bio-geochemical processes will have far reaching benefits to the science as a whole. As early as 1862, Friedrich Albert Fallon wrote Ž Sparks 1988. : A there is nothing in the whole nature which is more important or deserÕes much attention as the soil. Truly it is the soil which nourishes and proÕides for the whole nature, the whole of creation depends on the soil, which is the ultimate foundation of our existence.B The objective of this paper is to highlight some major development in soil science in the last four decades. The voluminous amount of contributions testifies to this and at the same time makes it difficult to suggest any individual contribution that had significant impact. Consequently, we approach the subject by considering major global issues and how the science responded to addressing them. 2. Basic studies 2.1. Soil surÕey and mapping Most western countries continued their national soil survey program after the Second World War. The decision in 1961, of the Food and Agriculture Organisation ŽFAO. of the United Nations with funding support from the United Nations Educational, Scientific and Cultural Organisation Ž UNESCO. , to document the global soil resources was a monumental step Ž FAO-UNESCO, 1974. . This propelled soil science to the forefront of agriculture, particularly in the areas of soil assessment and methods of soil analysis Ž van Baren et al., 2000. . After the Second World War, the dire need of the colonial powers for natural

406

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

resources was a major reason for initiating these kinds of investments in developing countries. The University and research systems in the Western world were mobilised to provide the background scientific information to backstop the international activities. Whatever the motivation, the result was a systematic effort to document global soil resources and better understand the factors and processes controlling soil formation and crop productivity. The FAO-UNESCO Ž 1974. Soil Map of the World is perhaps a benchmark event. The work not only rallied soil scientists from around the world for a common cause but also in the process helped provide information of global soil resources. Today, it is the only global digital database on global soils and its significance becomes more important when one realises that a similar effort may not happen in the near future. By the end of the 20th Century, there were many national systems of classification, methods of soil analysis, and even definition of terms that did not have an international acceptance. For example, the term clay has different size limits in the former Soviet countries Ž - 1 mm. in comparison to the rest of the world Ž- 2 mm. and organic carbon was measured by different methods. Many of these anomalies still remain although there is a concerted effort to harmonise the concepts, terms, and methods. Through the efforts of the International Union of Soil Sciences Ž IUSS. and with the collaboration of FAO and other institutions ŽIUSS, Working Group RB. , the World Reference Base Ž WRB. for soil classification is becoming the de facto classification system Ž ISSS Working Group RB, 1998.. The International Union of Science now accepts soil science as a science. During the last decade, information technology, specifically the use of Geographic Information Systems ŽGIS. and database management systems, is dramatically improving the presentation and use of soil survey information. There are developments for the in-situ measurement of some soil properties and such instrumentation is essential for monitoring of critical parameters. Information technology in the form of data-loggers and other equipment is facilitating the soil survey process. Manual cartography is being eliminated. Map analysis with fuzzy logic or other spatial analysis programs, which were rarely done in the past, provides a new means of quality control and validation. Rational assessment of land resources has taken a new turn. A new series of soil maps are now produced using all the existing information. Eswaran et al. Ž1997. have produced several different small-scale maps for Africa including potential for sustainable development based on biophysical considerations. These maps are expected to be very useful for the countries in Africa and international communities, regarding where to concentrate investment to enhance the productivity of the soil resources in this continent. Table 1 shows the distribution of land as a function of soil quality, which is summarised from the land classification map. With the advent of rapid computers and information technology, modeling of processes is placing new demands on data and helping to test concepts and

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

407

Table 1 Distribution of land as a function of soil quality Žfrom Eswaran et al., 1997. Land classification area

Ž=1000 km2 .

Percentage

Prime land High potential Medium potential Low potential Unsustainable Inland water TOTAL

2928 2051 3936 4736 16,727 273 30,650

9.6 6.7 12.8 15.5 54.6 0.9 100.0

facilitate applications. The Winand Staring Centre in the Netherlands carried out a first assessment of the state of nutrient depletion in Sub-Saharan Africa ŽStoorvogel and Smaling, 1990.. Nutrient balances were calculated, through a computer prediction model, for the arable lands of total 38 countries in SSA. The prediction were made for 1983 and the year 2000, for each country, based on data on the net removal of macronutrients from the major root zone layer. A simple model was established for the purpose of simulating the processes of nutrient inputs and outputs from the soil. This study showed that the nutrient depletion is quite high. Several other models, including crop models, are synthesizing information for policy makers and land users and thus serving the society that supported the science. Due to the fact that a new set of clients now value soil information, the demand for more and better information has increased and information delivered in a more timely manner is being demanded. Ironically, this is only in the developed world. In the developing world, funding and facilities hamper such progress. The enviro-centric world is also demanding monitoring of systems. The state of the nation’s land resources is only monitored in a few countries. Through the efforts of the Convention to Combat Desertification, monitoring of the land resource base may become a more routine process. 2.2. Information system and communication Data from CABI and ISI show that the annual output is about 10,000 soil science publications, out of which about 70% are in English and about 100 are monographs and textbooks ŽHartemink, 1999. . There is now a large number of national and international journals specialised in soil science, about 60 being most important in publishing more frequently cited research results Ž McDonald, 1994.. According to Yaalon and Arnold Ž 2000. the interest in soil science has also increased as shown by the increase in the membership of the IUSS. About 50,000 soil scientists, employed mostly in agronomic institutions are working in all aspects of soils. Yet only about 5% of the global agricultural research budget is allocated to soil research ŽYaalon, 2000. .

408

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

In the early 1960s, some 23% of all internationally published research papers were produced in the Soviet Union ŽYaalon, 1999. . Political changes in the former Soviet system and reduced purchasing power is reflected in the declining contribution from the Russians. Language is still an important barrier in the use of information generated in the different countries. By examining the literature we see that Europeans rarely cite American publication or visa versa Ž Yaalon, 1999.. This is true for other nationally published documents. Periodic state-ofthe-art reviews circumvent these constraints. Many national journals are also including abstracts in English and some of the other languages and this alleviates the situation. Information technology has not only enhanced the capability of manipulating information but has also dramatically increased the demand for data Ž van Engelen et al., 2000. . Simulation models require geo-referenced data for their effective application. Information technology is being successfully used in data-rich environments of the Western world. In the data-sparse situation of developing countries, they are less frequently applied or estimates made with default values Ž Eswaran et al., 2000. . The latter situation frequently results in erroneous assessments. Harmonising data requirements for models is still a constraint, which however is being addressed through collaboration between scientists and institutions. 2.3. Soil technology To replace or reduce the amount of commercial fertiliser application, alternative crop production techniques, such as the use of organic fertilisation and other organic inputs have been tested. This includes the use of legume species Ž green manure., manure compost, sewage sludge, wood chips, and peat, beside crop residues. Crop rotation, i.e. introduction of forages and legumes that have extensive rooting systems leave large amounts of organic matter, is also used by farmers as a technique. Three technologies Ž conservation tillage, agroforestry and precision agriculture., developed within the last two decades and representing major changes in land management, are elaborated here. 2.3.1. ConserÕation tillage No tillage or conservation tillage ŽCT. represents the most dramatic change in soil management in modern history of agriculture Ž Bradford and Peterson, 2000.. This technique has a great economic value and crop production can be achieved with minimal erosion risk. It was introduced in North America and is now widely used in South America, Australia, and, to lesser extent, in Europe. About 37% of the land farmed in the USA is now managed with a CT system, including no till, minimum till, or ridge till Ž Reicosky et al., 1995; Grant, 1997; Lal et al., 1999..

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

409

2.3.2. Agroforestry This system has emerged in the 1980s and is a combination of fast growing trees with agriculture that also includes feed to support livestock Ž Mergen, 1986.. It provides habitat for bio-diversity and produces goods and services ŽWinterbottom and Hazelwood, 1987. . Certain practices increase carbon sequestration substantially ŽUnruh et al., 1993; Schroeder, 1993. . The International Centre for Research in Agroforestry in Nairobi, Kenya is a lead institution dedicated to this technology ŽSanchez et al., 1997. . 2.3.3. Precision agriculture The technique is a site-specific soil management technology Ž Sims, 2000. . Intensive soil sampling combined with geostatistics and modelling Ž Viscarra and McBratney, 1998. are prerequisites. Computerisation of all aspects of management makes this technique the most advanced and scientific approach to farming. The fact that it is also profitable and addresses many of the environmental concerns indicates a new era of agriculture. 2.4. Soil microscopy (micromorphology and micromorphometry) Microscopic techniques enabled the in vitro study of soils. Miedema and Mermut Ž1990. showed that there were about 1750 references, which include books, proceedings and individual papers published during the period 1960– 1990. Much of the post-war work on micromorphology was focused on improving the quality of thin-sections and developing terms and schemes for descriptions and interpretation ŽJongerius and Heinzberger, 1975. . Building on the terminology introduced by Kubiena, Brewer Ž 1964, 1976. , FitzPatrick Ž 1984. and eventually Bullock et al. Ž1985., the terminology was systematically refined. A valuable publication for this process was the Glossary of Micromorphology published by Jongerius and Rutherford Ž 1979. . The advent of the Scanning Electron Microscope Ž SEM. and the electron microprobe extended the power of magnification and enabled the analysis of very small areas of the particle or surface Ž Smart and Tovey, 1982. . Pioneering work on this was done at the University of Gent in Belgium using the SEM ŽEswaran and Joseph, 1974; Eswaran and Stoops, 1979. and microprobe analysis ŽBisdom, 1981. at the Soil Survey Institute Ž STIBOKA. at Wageningen, Netherlands. The sub-microscopic analysis added a new dimension to the understanding of soils. In addition to elaborating on structure, patterns, and results of soil formation, the technique was extensively used to evaluate mineral alteration Ž Stoops and Dalvigne, 1990.. In North America and specifically in the United States, the new Soil Taxonomy ŽSoil Survey Staff, 1975. required correct placement and soil micromorphological analyses was heavily relied upon. In the last two decades, the techniques have been used by other sciences, specifically archaeology.

410

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

Quantification of the fabric of soils and its components was a major challenge. The use of the image analyses in soil science was a major breakthrough. The application of this technique was initiated at the Netherlands Soil Survey Institute ŽJongerius et al., 1972.. With the availability of new computer technology, image analysis has entered a new era in the last two decades Ž Protz et al., 1987; Mermut and Norton, 1992.. 2.5. Pedology and classification of soils The 50 years of progress made in soil genesis, classification and cartography, since the creation of the International Society of Soil Science in 1924, was summarised by Kellogg Ž1974. in a special issue of Geoderma Ž 1974. . The workable concepts of soils that made it possible to understand the genesis, classification, and mapping were already developed before 1924. Their application to farming, forestry, and engineering were greatly improved during the 1920s and 1930s. To quantify changes in the soil system, a new concept, which is called pedometrics, is now introduced. Webster Ž 1994. describes it as essentially the application of probability and statistics to soils. Pedometrics, though still a research tool, has the potential to complement conventional soil surveys and a crucial technique in precision agriculture. Major advances in soil classification took place in the 1970s and 1980s and since then have slowed down. The early classification systems did not have quantitative definitions and were not rigid in their structure. Soil Taxonomy ŽSoil Survey Staff, 1999. was the first system to quantitatively define the diagnostic horizons and introduce a Key to the classification of soils. There was little appreciation for this from the European community but with time, the terms, definitions, and even the structure of Soil Taxonomy was being replicated in other systems, such as the Chinese Soil Taxonomy currently being developed. Modern concept of soil genesis and major advances in soil classification came about in the last half of the 20th century. The forces that shaped these developments included: Ø developments in science and technology, Ø a general increase in wealth of the industrial nations, and Ø the cold war that prompted the desire to know about the natural resources of all nations. With the advent of the WRB, other parallel systems are being developed ŽFAOrISRICrISSS, 1998.. The French have developed the A La Base Referential du Classification du SolsB, Russians are re-evaluating their system, and other countries are embarking to develop or enhance their national systems. In the United states, a second edition of Soil Taxonomy was published in 1999

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

411

ŽSoil Survey Staff, 1999. . A good review of some of the recent efforts is given by Spaargaren Ž 2000. . A major concern is the need of the future and the design of systems in the context of advances in information technology. Nachtergaele Ž 2000. has summarised the progress made on the soil map of the world for the last 40 years. All national and international institutions agree that there is a definite need for soil information to cope with sustainable land use and crop production ŽAlexandratos, 1995. . Nachtergaele Ž 2000. indicates that good progress was made between 1993 and 1996 on the systematic storage and correlation of soil resource information on a worldwide scale, in the format of Global Soil and Terrain Digital Database Ž SOTER. as well as the establishment of an international Soil Profile Database. A debate that is underway stems from the fact that there will be no attempt to make a global soil map in the foreseeable future. In addition, some desire exists for a global map at a scale of 1:1 million. The SOTER program of FAO and ISRIC is designed to address these questions. The SOTER, despite its value, is an under-funded effort and consequently its progress is limited. In many of the countries, there are few or no detailed farm-level soil maps. With the exception of the richer countries, systematic national program for mapping soils does not exist. This presents great problems in technology transfer, and for other purposes of soil information. Despite a global concern of land degradation and desertification, location specific information on land quality is not available in most countries. A dichotomy thus exists between developments in global policies and actual information available at the farm level. Little progress can be made if this issue is not brought to the forefront of development assistance. 2.6. Soil components (minerals and organics) Much of the chemistry and physics of soil components are discussed by Sparks and Raats of this issue. Our aim here is to touch some development of studying the soil components. Research works in this period have resulted in significant contributions to understanding of soil genesis, soil physical properties, the formation and dynamics of organic matter, interaction of agro-chemicals Žpesticides, fertilizers. with soil components, availability of plant nutrients, and environmental protection Ž Mermut and Eswaran, 1997. . These have gradually provided an opportunity to integrate the knowledge on soil minerals with organics and microbes ŽHuang and Schnitzer, 1986. . Developments in instrumentation have contributed to the advancement of understanding the soil components and this will continue. These includes X-ray diffractometry, Fourier transform infrared Ž FTIR. , nuclear magnetic resonance ŽNMR., Mossbauer spectroscopy, X-ray Photo electron spectroscopy Ž XPS. , Auger electron spectroscopy Ž AES., atomic force microscopy Ž AFM. , scanning probe microscopy Ž SPM. , several varieties of electron microscope, etc. Their use

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

412

in studies related to soil components has resulted in impressive information about the surface characteristics of the soil component at atomic levels Ž Sparks, 2000.. The role of minerals on the dynamics and fate of toxic pollutants is just recently appreciated and major emphasis of soil mineralogy in the next half century and beyond will be the behaviour of soil component from the point of environmental protection and sustainability. Advancement in modern instrumentation has also helped in understanding the organic soil components. Solid state 13 C nuclear magnetic resonance spectroscopy Ž 13 C NMR., FTIR, and analytical pyrolysis are the instruments currently in use to probe the chemical structure of soil organic carbon. The greatest advantage of NMR and FTIR is their ability to characterise the chemical structure of organic matter in-situ and non-destructively Ž Benke et al., 1998; Baldock and Nelson, 2000.. 3. Application 3.1. Soil fertility and management Soil fertility has emerged to serve the needs of production agriculture. The efforts in the soil fertility area were basically concentrated around: Ø Ø Ø Ø Ø Ø Ø

the factors that control the availability of essential elements in soils, soil and tissue tests for assessing nutrient levels, interaction of nutrients with soil components, nutrient cycling, application methods of fertilisers, optimisation of soil fertility for sustainable crop production, and development of soil management techniques for efficient use of nutrients.

Several new technologies that emerged Ž Section 2.3. in the last decade have the potential to significantly alter soil fertility management Ž Hergert, 1997; Sims, 2000.. In the past 50 years, the concept on fertility of tropical agriculture has gradually evolved and they are not uniformly considered as marginal soils due to low acidity and lack of plant nutrients ŽSanchez and Buol, 1975. . Nutrients are becoming recognised as capital and the World Bank is embarking new programs in Africa called the Soil Fertility Initiative Ž SFI. Ž Donovan and Casey, 1998. . Other international organisations involved in the initiative are FAO, ICRAF, IFDC, IFA and IFPRI. The SFI was officially launched during the World Food Summit, November 1996. The SFI activities are expected to result in short-term economic benefits to farmers as well as in the longer-term restoration of the nutrient capital in the soil. Policy and institutional improvements are essential to the success of SFI.

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

413

Processes of diffusion and mass flow of the nutrients in the rhizosphere became more clear in the 1970s and 1980s Ž Barber, 1984. . However, it is now established that each plant has its own influence on the immediate root environment, suggesting the need for further research for understanding the root rhizosphere. There is also a lot of room for the development of methodology. We just started to understand the ion supply rate to plants, using ion exchange resin membrane ŽQian et al., 1992.. In spite of the success, the yields are frequently below the potential, especially in Africa. Poor soil water and nutrient management are the recognised cause of this ŽGreenland et al., 1994.. The report on expansion of the consultative Group on International Agricultural Research Ž TAC, 1993. states that Athe past neglect of research on conservation and management of natural resources must be addressed and higher priority given to both technical and socio-economic aspect of sustainability. Soil fertility research is an integral part of the quest for sustainable agriculture, but the classical research must be supplemented by innovative work complementing soil–water–crop simulation models.B 3.2. EnÕironmental pollution The concern today is the large quantities of pollutants generated by humans and the overloading of ecosystem components with toxic materials. Environmental pollution and its effects on human health and other living beings are now a very serious public concern ŽBrendecke and Pepper, 1996. . A special journal was created by the SSSA in 1971. Worldwide input of metals into soils is given in Table 2 Ž Nriagu and Pacyna, 1988.. In fact, only a few places on earth are free of heavy metal pollution. Discoveries of synthetic organic pesticides in the middle of the 20th century made it possible to use a wide range of these chemicals in agriculture within the past few decades. It is claimed that without chemical weed control, minimum tillage would not be economical ŽOdum, 1971.. Increasing environmental consciousness and willingness of the society to reduce such pollution provided important funding for research and development activities. For instance, groundwater contamination and increased level of toxicity in soils have become a worldwide concern and has led to considerable research on the transport of pollutants through porous media. Much research is needed in this area Ž Sawhney and Brown, 1989.. A large number of methodologies have been made available with respect to cleaning of contaminated soils Ž Noyes Data, 1991. . Bioremediation appears to be one of the techniques, currently tested, to clean organic and metal pollutants from the soil ŽMoffat, 1995; Skipper and Turco, 1995. . Agricultural application of A sewage sludgeB is now a common practice, for both practical and economic reasons. The presence of toxic metals in these residues can affect plants, ground and surface waters, and human health through

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

414

Table 2 Worldwide inputs of some heavy elements into soils Žfrom Nriagu and Pacyna, 1988. Sourcea

Heavy elements, 1000 tonnesryear Cd

Cr

Cu

Agricultural and 2.2 82 67 animal wastes Logging and wood waste 1.1 10 28 Urban refuse 4.2 20 26 Municipal sewage and 0.18 6.5 13 organic waste Solid wastes from metal 0.04 1.5 4.3 fabrication Coal ashes 7.2 298 214 Fertilizers and peat 0.20 0.32 1.4 Discarded manufactured 1.2 458 592 products Atmospheric fallout 5.3 22 25 TOTAL input 26.0 898 9.71 a

Pb 26

Mn

Hg

158

Mo

0.85 34

Ni 45

Zn 316

7.4 40 7.1

61 1.10 24 0.13 8.1 0.44

1.6 2.3 0.43

13 6.1 15.0

39 60 39

7.6

2.6 0.04

0.08

1.7

11

144 1076 2.9 12 292 300

2.6 44 168.0 0.01 0.46 2.2 0.68 1.9 19

232 759

2.5 8.3

27 1669

2.3 87

24 294

298 2.5 465 92 1322

These inputs exclude tailings and slags at the smelter sites.

the food chain ŽLamy et al., 1993.. High concentrations of fertilisers, such as NO 3 –N and, phosphorous in soils and groundwater are mainly due to agricultural practices. A major concern with fertilisers, especially P fertilizers is the presence of the trace elements ŽMortvedt et al., 1981. . Mermut et al. Ž 1996. showed that considerable amounts of Co, As, Cd, Ni, Cu, Zn, Mo, V, Cr, Sb, Tl, Pb, and U are present in P fertilisers and part of these elements are bioavailable. In areas where combustion of fossil fuels smelting of ores Ž especially sulfides. and release of nitrogen oxides to the air are exercised, the pH of the rain water drops to nearly 2.0. This is the reason why acid rains or acidification is considered as a potential hazard by environmentalists. The term acid rain was used in the 19th Century to describe rain in industrialized part of north-west England Ž Wild, 1994. . For the last two decades scientists have called attention to increased acidity in rainwater. Normal rainwater has a pH of about 5.6. In areas where large scale combustion of fossil fuels is used, especially with smelting of sulfide ores, the pH of the rainwater drops to nearly 2.0. Soils generally have sufficient buffering capacity to accommodate the influence of acid rains. 3.3. Land degradation and sustainability There have been increasing concerns around the World, including FAO–UN, for the initiation of a global strategy to assist nations in developing methods and policies to combat land degradation. It is indeed an important concern affecting

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

415

the wealth of nations, food security and impacting the livelihood of almost every person on earth ŽEswaran and Beinroth, 1996. . AGENDA 21 of the United nations Conference on environment and development Ž United Nations Conference on Environment and Development, 1992. emphasises the need, and proposes a wide range of activities, to address land degradation in general and desertification in particular. 3.3.1. Historic deÕelopment Since the declaration of the United Nation Conference on Human Environment in Stockholm in 1972, there have been numerous global conferences, which have provided strategies to achieve sustainable land management, where the control of land degradation has been a major concern Ž FAO, 1979. . Following Stockholm, some of the other major conferences are: Ø The World Charter for Nature 1982 Ø The Rio de Janeiro Declaration on Environment and Development 1992, Agenda 21 Ø The United Nation Convention to Combat Desertification, 1994 Ø The convention on Biological diversity, 1995 Ø The United Nation Framework Convention on Climate Change 1995, and Ø The World Food Summit, FAO, Rome 1996. Documents of the above mentioned conventions have been used around the world to reform laws and policies for the sustainable use of the natural resources. However, many Asoil associations and organisationsB have raised the benefits of a specific convention for the AsoilB, and in doing so, they have pointed out that soil is a more complex medium than air or water and may be the most complex system known to science. The URL for this convention, known as Tutzing Project, is: http:rrwww.soil-convention.orgr. FAO has developed a provisional methodology for the assessment and mapping of land degradation on the global scale Ž FAO, 1971, 1979; FAO-UNEP, 1978, 1983.. Two types of assessments were considered, i.e. present degradation and degradation at risk. The six groups of land degradation recognised were water erosion, wind erosion, excessive salts, chemical degradation, physical degradation, and biological degradation. This was followed by developing a methodology for the assessment and mapping of land degradation Ž FAO, 1984. . Based on a discussion paper, entitled ATowards a Global Soil Resources InventoryB at scale 1:1 million by Sombroek Ž1984., ISSS has organised a workshop in January 1986 in Wageningen, the Netherlands. A project proposal was prepared for the World Soils and Terrain Digital Data Base Ž SOTER. ŽISSS, 1986. during the 13th Congress of the International Society Soil Science ŽISSS. in 1986 ŽHamburg, Germany. . This initiative, which is called the AGlobal and National Soils and Terrain Digital Database Ž SOTER.B, was officially

416

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

adopted at that time. Under a United Nations Environmental Program Ž UNEP. project, International Soil Reference and Information Centre Ž ISRIC. has developed a methodology for SOTER, in close cooperation with the Agriculture Canada Land Resource Research Centre, FAO, and ISSS. The test results of SOTER were reported at the 14th ISSS Congress in Kyoto, Japan in 1990. In 1995 ISRIC, UNEP, and FAO agreed to produce a 1:5 million scale, using the SOTER approach for the 17th IUSS Congress in 2002 in Thailand. Oldeman et al. Ž1991. evaluated global human-induced soil degradation; although somewhat subjective, it provided information on the current magnitude of the soil degradation problems in the world. Information is based on the collective opinion of a few individuals with very little measurements to support their findings. 3.3.2. Global dimension Assessment of the extent of soil degradation has been attempted at the global level Ž 1:5, 1:10 million. . Since the United Nation Conference of the human environment held in Stockholm in 1972, attempts were made to develop methodologies for assessment and mapping of degradation and desertification ŽFAO, 1979, 1984.. The International Soil Reference and Information Centre ŽISRIC., under the aegis of UNEP and in collaboration with FAO, has produced a World Map of the Status of Human-Induced Soil Degradation at a scale of 1:10 million Ž Oldeman et al., 1991. known as GLASOD. It identifies four degrees of degradation Ž light, moderate, strong and extreme. . Five types of human intervention were identified that result in soil degradation. These are: 1. 2. 3. 4.

deforestation and removal of natural vegetation Ž 579 million ha. , overgrazing of vegetation by livestock Ž 679 million ha. , improper management of agricultural land Ž 552 million ha. , over exploitation of vegetative cover for domestic use Ž 133 million ha. , and 5. industrial activities leading to chemical pollution Ž 32 million ha. . According to GLASOD, 1964 million ha of agricultural land worldwide are degraded Ž Table 3.. While it is useful, however, such a global assessment is not enough, if effective programs or policy measures have to be implemented in a given country to address mitigation technologies. Attempts were made by various organisations to address this issue. Young Ž1998. reports that: Ø about 5% of the agricultural land in developing countries has been lost by degradation, Ø productivity has been appreciably reduced on a further 25%, Ø Some 10% of irrigated land is severely salinized,

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

417

Table 3 Human-induced soil degradation for the world ŽGLASOD. ŽOldeman et al., 1991. Type

Light Moderate Strong Extreme Total Total Žmillion ha. Žmillion ha. Žmillion ha. Žmillion ha. Žmillion ha. Ž%.

Loss of topsoil Terrain deformation WATER Loss of topsoil Terrain deformation Overblowing WIND Loss of nutrients Salinization Pollution Acidification CHEMICAL Compaction Waterlogging Subsidence of organic soils PHYSICAL TOTAL Žmillion ha. Žpercent.

301.2 42.0 343.2 230.5 38.1 – 268.6 52.4 34.8 4.1 1.7 93.0 34.8 6.0 3.4

454.5 72.2 526.7 213.5 30.0 10.1 253.6 63.1 20.4 17.1 2.7 103.3 22.1 3.7 1.0

161.2 56.0 217.2 9.4 14.4 0.5 24.3 19.8 20.3 0.5 1.3 41.9 11.3 0.8 0.2

44.2

26.8

12.3

749.0 38.1

910.5 46.1

295.7 15.1

3.8 2.8 6.6 0.9 – 1.0 1.9 – 0.8 – – 0.8 – – – – 9.3 0.5

920.3 173.3 1093.7 452.2 82.5 11.6 548.3 135.3 76.3 21.8 5.7 239.1 68.2 10.5 4.6 83.3 1964.4

55.7

27.9

12.2

4.2 100

Ø the limits to water availability has been reached in semi-arid zones, and Ø over the past 10 years, forest cover in the tropical region has been lost 0.8% a year Based on the existing information, international programs, protocols, conventions, and treaties are now placing more emphasis on soil degradation and desertification than ever before. Planet earth is being hurt and soil science is one of the sciences that can help the location of the afflicted areas and provide remedial technologies. If at all, this will be the greatest challenge and can be the most important role for soil scientists in this new century. 3.4. Soil quality and sustainability The concept of soil quality is very new and continues to evolve Ž Doran et al., 1994.. The concept is developed to characterise the usefulness and health of soils. It is recognised as a compound measure that cannot be measured directly. Current discussion on soil quality is focused on soil characteristics that should be taken into consideration. A minimum data set of soil characteristics must be selected and quantified ŽSinger and Ewing, 2000. . Smith et al. Ž 1994. claims

418

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

that soil quality is the most important factor for the sustainability of the biosphere. These authors have suggested a multiple variable indicator Ž MVIT. that could be used to produce probability maps, and they outline the procedure. Several soil and land quality index or indicators have been suggested Ž Paar et al., 1992; FAO, 1997.. Better understanding of soil quality is fundamental for rehabilitation of degraded soil and environment. 3.5. Carbon cycle and sequestration Carbon is one of the essential components of life and has very important functions in the soil system. The studies related to estimate global organic carbon and its cycle has a rather short history Ž Buringh, 1984. . Eswaran et al. Ž1993. stressed the needs for a more accurate estimate of global carbon pools. The total amount of carbon stored in terrestrial ecosystems is large. According to Eswaran et al. Ž 1999. , the organic carbon stocks in soils is about 1526 Pg while the inorganic carbon stocks is about 756 Pg. The rate of the process is estimated to be ; 2 Pg Cryear Žabout 0.1% of the current storage in the soil. , but this is an estimate as yet. About 75% of terrestrial carbon occur in the soil, as the above ground carbon is estimated to be 500 Pg. Therefore, they are essential in terms of carbon sequestration. The cycle of carbon in the soil is shown in Fig. 1. Atmospheric measurements of CO 2 concentration show that there is indeed an increase of CO 2 in the atmosphere, from 290 ppm before the Industrial Revolution to over 360 ppm today. Total atmospheric carbon is estimated to 750 Pg ŽLeggett, 1990.. Fig. 1 shows the dynamics of carbon transformations and transport in the soil Ž United States Department of Energy, 1999. . Some estimates are made on the current rate of the transformation, but hard data are not yet available. However, this kind of illustration provides an opportunity to develop ideas as to how to deal with excess atmospheric carbon in terms of terrestrial environment. In the past decade, increasing awareness of CO 2 build-up in the atmosphere and the threat of global warming has instigated society to find means to reduce atmospheric CO 2 . The concept of greenhouse gas reduction by sequestering carbon in different terrestrial ecosystems, or withdrawal of CO 2 from the atmosphere, has been extensively discussed. While the debate on complex issues of quantification of carbon stocks is still going on, it is generally agreed that carbon sequestration can be a highly cost effective and environmentally sound mitigation technique. This would also be a response to commitments by signing parties under the conventions of: Ži. Climate Change Ž Kyoto Protocol. ; Žii. Biological Diversity; and Žiii. Combating Desertification.

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

419

Fig. 1. The dynamics of carbon transformations and transport in the soil ŽUnited States Department of Energy, 1999..

Therefore, strategies that could lead to the amelioration of these problems are likely to be of great global significance. The potential for carbon sequestration appears to be large in comparison with current rate for terrestrial ecosystems Ž 5–10 Pg Cryear, when all terrestrial ecosystems are considered. . What is the maximum capacity to sequester carbon is not yet known. There are two fundamental approaches to sequestering carbon: Ži. Protection of ecosystem that stores carbon so that sequestration can be maintained Ž increasing residence time. , and Žii. Manipulations of ecosystems to increase carbon sequestration beyond the current conditions. According to UNEP Ž 1997. , dryland stores 60 times more carbon than the carbon added to atmosphere by fossil fuel. Drylands cover a 450 million ha area. A small change in the rate of carbon sequestered in dryland regions can have large impacts on CO 2 in the atmosphere. Over 1 billion people currently live in

420

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

susceptible drylands and any effort to restore productivity of these eco-regions will be of benefit for their inhabitants. One of the fundamental arguments is that about 50% of SOM is lost in the top soil, due to intensive agricultural practices. Uncultivated soils were in equilibrium with the native vegetation and accumulated large SOC reserves and cultivation have disrupted the steady-state equilibrium Ž Lal et al., 1999. . There are reliable estimates that many cultivated soils in North America have lost substantial amount of SOM in cultivated lands Ž Acton and Gregorich, 1995; Bruce et al., 1999., which resulted in decline in production, increased soil erosion and soil degradation. The lost carbon primarily should be returned to the soil. It is estimated that this will take 25–50 years, with current technologies ŽLal et al., 1998.. With good management practices, it may be possible to exceed the original native SOM content of many soils. Lal et al. Ž1999. suggest that intensification of agriculture on good soils can be achieved through the widespread adoption of: Ži. conservation tillage and residue management, Žii. irrigation and water management systems, Žiii. improved cropping systems, including agroforestry.

3.6. Societal affairs In the past, soil functions and their relevance to the society are mentioned only sporadically. Multiple role and functions of soils have became known in recent years ŽYaalon and Arnold, 2000.. With research and development of new technologies, we also recently became conscious of the limitations of soils resources. Increasing damaging effects on the environment by humans will increase basic and applied studies involving soils Ž Yaalon, 1999. . Societal relevance or services of soils to mankind is growing. These services are becoming better understood and appreciated. Symposia and conferences on this topic to increase the public awareness of the goods and services provided by the soil science community are needed. With the new millennium, the International Society of Soil Science has become the International Union of Soil Sciences and restructured itself to include the role of soils in the society. Recognition of the societal affairs as a new separate Commission is a big step towards the future development in this area. Increasing need for a sustainable soil use treaty or internationally supported soil convention is currently under discussion. As new sub-disciplines gradually emerge, Gardner Ž 1991. suggested that soil science could be more effective in the society if different sub-disciplines of soil science are integrated. A lot can be achieved with this integration. Simonson

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

421

Ž1991. pointed out the need to create a more accurate public image of soil science.

4. Conclusion Soil science was developed to enhance agriculture and forestry production. Initially, it relied on ancillary sciences for its techniques and applications but with time, it has emerged as a discipline by itself with its own set of terminology and classification. In the last few decades, it has refined tools or adapted tools for its own purposes. In the process of investigating the soil resource, a major contribution has been the better understanding of the major component of the ecosystem. By keeping pace with agronomy and crop sciences, it has been an effective partner towards the goal of food production and the sustainable use of the land resources. The profusion of sub-disciplines in the science, as has been illustrated, is not only a mark of the progress but also an attempt to unravel the complexity of the soil. Studies, particularly during the last two decades, are pointing to a variety of negative impacts to global ecosystems, resulting in the decline in land quality, global warming, and even disappearance of species of plants and animals. As a result, there is considerable effort from the global to the local to study the conditions, causes for the changes, and remedial technologies to address the changes. Internationally, the quest to increase food production is being replaced by a strong commitment to protect and preserve the environment. Soil science has responded to this new demand of society and is using its collective experience and knowledge base to assist. This is the immediate challenge of the new millennium and the science has been responsive and effective. Over a longer time frame, questions of food security and the ability of the tropical countries to feed themselves will remain. Most assessments of land resources of developing countries show that they are highly degraded or degrading at rapid rates. Rehabilitating such lands, exploiting their resilience if any, enabling some of the countries to attain sustainability and all of these in a context of maintaining or enhancing the integrity of the environment are the tasks ahead. No one discipline can provide the needed answers and hence a multi-disciplinary approach where soil scientists work with ecologists and social scientists will become the norm. At the turn of the century and despite the remarkable contributions of soil science, investments in teaching and research is declining. Soil survey organisations are being downsized or eliminated. Soil science departments in universities are or have been merged with other disciplines and there is a measurable decrease in the emphasis on the science. Research funds for basic research in the science have dwindled. Keeping the science alive and enabling the science to

422

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

contribute to the new challenges of managing land resources become the challenges to address. This is a responsibility of society but soil scientists must play their role of demonstrating the value of the science.

References Acton, D.F., Gregorich, L.J., 1995. The health of our soils, towards the sustainable agriculture in Canada. Agriculture and Agri-Food Canada, Research Branch. Center for Land and Biological Resources Publ. 1906rE. Alexandratos, N., 1995. World Agriculture: Towards 2010. An FAO study. FAO and Wiley, New York, NY. Baldock, J.A., Nelson, P.N., 2000. Soil organic matter. In: Sumner, M.E. ŽEd.., Handbook of Soil Science. CRC Press, Boca Raton, pp. B25–B84. Barber, S.A., 1984. Soil Nutrient Bioavailability. Wiley, New York, NY. Benke, M.B., Mermut, A.R., Chatson, B., 1998. Carbon C-13 CPrMAS NMR and DR-FTIR spectroscopic studies of sugarcane distillery waste. Can. J. Soil Sci. 78, 227–236. Bisdom, E.B.A. ŽEd.., 1981. Submicroscopy of Soils and Weathered Rocks. PODOC, Wageningen, The Netherlands. Bradford, J.M., Peterson, G.A., 2000. Conservation tillage. In: Sumner, M.E. ŽEd.., Handbook of Soil Science. CRC Press, Boca Raton, pp. G247–G298. Brendecke, J.W., Pepper, I.L., 1996. The extent of global pollution. In: Pepper, I.L., Gerba, C.P., Brusseau, J.L. ŽEds.., Pollution Science. Academic Press, New York, pp. 3–8, Chap. 1. Brewer, R., 1964. Fabric and Mineral Analysis of the Soils. Wiley, New York. Brewer, R., 1976. Fabric and Mineral Analysis of the Soils. Robert E. Kriger Publ., Huntingdon, NY. Bruce, J.P., Frome, M., Haites, E., Janzen, H., Lal, R., Paustian, K., 1999. Carbon sequestration in soils. J. Soil Water Cons. 54, 382–389. Bullock, P., Fedoroff, N., Jongerius, A., Stoops, G., Tursina, T., Babel, U., 1985. Handbook for Soil Thin Section Description. Waine Research Publications, Wolverhampton, UK. Buringh, P., 1984. Organic carbon in soils of the world. In: Woodwell, G.M. ŽEd.., The Role of Terrestrial Vegetation in the Global Carbon Cycle: Measurement by Remote Sensing. Wiley, Chichester, UK, pp. 91–109. Donovan, G., Casey, F., 1998. Soil Fertility Management in Sub Saharan Africa. World Bank Technical Paper No. 408, Washington, DC. Doran, J.W., Coleman, D.C., Bezdicek, D.F., Stewart, B.A. ŽEds.., 1994. Defining soil quality for sustainable environment. Soil Science Society of America, Madison, WI, Special Publ. No. 35. Eswaran, H., Beinroth, F.H., 1996. Land degradation: issues and challenges. Abstracts, First International Land Degradation Conference, Adana, Turkey, 10–14 June 1996. University Cukurova, Department of Soil Science, Adana, Turkey, p. 1. Eswaran, H., Joseph, K.T., 1974. Pyrite and its oxidation products in an acid-sulfate soil MARDI. Res. Bull. 20, 50–57. Eswaran, H., Stoops, G., 1979. Surface textures of quartz in tropical soils. Soil Sci. Soc. Am. J. 43, 420–424. Eswaran, H., van den Bergh, E., Reich, P.F., 1993. Organic carbon in soil of the world. Soil Sci. Soc. Am. J. 57, 192–194. Eswaran, H., Almaraz, R., van den Berg, E., Reich, P., 1997. An assessment of the soil resources of Africa in relation to productivity. Geoderma 77, 1–18.

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

423

Eswaran, H., Reich, P.F., Kimble, J.M., Beinroth, F.H., Padmanabhan, E., Moncharoen, P., 1999. Global carbon stocks. In: Lal, R., Kimble, J.M., Eswaran, H., Stewart, B.A. ŽEds.., Global Climate Change and Pedogenic Carbonates. Lewis Publishers, Boca Raton, pp. 15–25. Eswaran, H., Beinroth, F.H., Virmani, S.M., 2000. Resource management domains: a biophysical unit for assessing and monitoring land quality. Agric., Ecosyst. Environ. 81, 155–162. FAO, 1971. Land degradation. Soil Bulletin No. 13, FAO, Rome. FAO, 1979. A provisional methodology for soil degradation assessment. FAO, Rome, ISBN 92-5-100869-8. FAO, 1984. A provisional methodology for assessment and mapping of desertification, FAO, Rome. FAO, 1997. Land quality indicators and their use in sustainable agriculture and rural development. Land Water Bull. 5, Rome. FAOrISRICrISSS, 1998. World reference base for soil resources. World Soil Resources Report 60, FAO, Rome. FAO-UNEP, 1978. Methodologies for Assessing Soil Degradation. FAO, Rome. FAO-UNEP, 1983. Guideline for the Control of Soil Degradation. FAO, Rome. FAO-UNESCO, 1974. Soil map of the world 1:5,000,000. Vol. I: Legend. UNESCO, Paris, France. FitzPatrick, E.A., 1984. Micromorphology of Soils. Chapman & Hall, London, UK. Gardner, W.R., 1991. Soil science as basic science. Soil Sci. 151, 2–6. Grant, F.R., 1997. Changes in soil organic matter under different tillage and rotations: mathematical modelling in ecosystems. Soil Sci. Soc. Am. J. 61, 1159–1175. Greenland, D.J., Bowen, G., Eswaran, H., Rhoades, R., Valentin, C., 1994. Soil, Water and Nutrient Management Research: A New Agenda. IBSRAM, Bangkok, Thailand. Hartemink, A.E., 1999. Publish or perish: Ž2. How much we write. Bull. Int. Union Soil Sci. 96, 16–23. Hergert, G.W., 1997. A futuristic view of soil and plant analysis an nutrient recommendations. Proceedings 5th International symposium Soil Plant Analyses, Minneapolis, MN. pp. 24–35. Huang, P.M., Schnitzer, M., 1986. Interaction of soil minerals with natural organics and microbes. SSSA Special Publication No. 16, Madison, WI. ISSS, 1986. World Soils and Terrain Digital Data Base ŽSOTER., Hamburg, Germany. ISSS Working Group RB, 1998. In: Deckers, J.A., Nachtergaele, F.O., Spaargaren, O.C. ŽEds.., World Reference Base for Soil Resources: Introduction. 1st edn. ISSS, ISRIC, FAO, Acco Leuven, Belgium, 165 pp. Jongerius, A., Heinzberger, G., 1975. Methods in soil micromorphology, a technique for the preparation of large thin section. Soil Survey Papers, vol. 10, Soil Survey Institute, Wageningen, The Netherlands. Jongerius, A., Rutherford, G.K., 1979. Glossary of Soil Micromorphology. Centre of Publication and Documentation, Wageningen, The Netherlands. Jongerius, A., Schoonderbeek, D., Jager, A., 1972. The application of Quantimet 720 in soil micromorphology. Microscope 20, 243–254. Kellogg, C., 1974. Soil genesis, classification and cartography: 1924–1974. Geoderma, 12, 347–362. Lal, R., Kimble, J.M., Follet, R.F., Cole, V.R., 1998. The Potential of U.S. Cropland to Sequester Carbon and Mitigate the Greenhouse Effect. Sleeping Bear Press, Ann Arbor, MI. Lal, R., Follet, R.F., Kimble, J.M., Cole, V.R., 1999. Managing U.S. cropland to sequester carbon in soil. J. Soil Water Cons. 54, 374–381. Lamy, I., Bourgeois, S., Bermond, A., 1993. Soil cadmium mobility as a consequence of sewage sludge disposal. J. Environ. Qual. 22, 731–737. Leggett, G. ŽEd.., 1990. Global warming. The Green Peace Report, Oxford Univ. Press.

424

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

Lubchenco, J., 1998. Entering the century of the environment: a new social contract for Science. Science 279, 491–497. McDonald, P. ŽEd.., 1994. The Literature of Soil Science. Cornell Univ. Press, Ithaca, NY. Mergen, F., 1986. Agroforestry—an overview and recommendations for possible improvements. Trop. Agric. 63, 6–9. Mermut, A.R., Eswaran, H., 1997. Opportunities for soil science in a milieu of reduced funds. Can. J. Soil Sci. 77, 1–7. Mermut, A.R., Norton, L.D., 1992. Digitization, processing and quantitative interpretation of image analyses in soil science and related areas. Geoderma 53 Ž3–4.. Mermut, A.R., Jain, J.C., Kerrich, R., Kozak, L., Jana, S., 1996. Influence of fertilizers on environmental trace element concentrations of soils in Saskatchewan. J. Environ. Qual. 25, 845–853. Miedema, R., Mermut, A.R., 1990. Soil Micromorphology: An Annotated Bibliography 1968– 1986. CAB International, Wallingford, Oxen, OX10 8DE, UK. Moffat, S.M., 1995. Plants proving their worth in toxic metal cleanup. Science 269, 302–303. Mortvedt, J.J., Mays, D.A., Osburn, G., 1981. Uptake by wheat of cadmium and other heavy metal contaminants in phosphate fertilizers. J. Environ. Qual. 10, 193–197. Nachtergaele, F.O., 2000. From the soil map of the world to the digital soil and terrain database: 1960–2002. In: Sumner, M.E. ŽEd.., Handbook of Soil Science. CRC Press, Boca Raton, pp. H-5–H-17. Noyes Data, 1991. In Situ Treatment of Hazardous Waste-contaminated Soils. 2nd edn. Park Ridge, NJ, USA. Nriagu, J.O., Pacyna, J.M., 1988. Quantitative assessment of worldwide contamination of air, water and soils with trace metals. Nature 333, 134–139. Odum, E.P., 1971. Fundamentals of Ecology. 3rd edn. W.B. Saunders, Philadelphia. Oldeman, L.R., Hakkeling, R.T.A., Sombroek, W.G., 1991. World Map of the Status of Human Induced Soil Degradation: An Explanatory Note. 2nd revised edn. ISRIC, Wageningen, The Netherlands. Paar, J.F., Papendick, R.I., Hornick, S.B., Meyer, R.E., 1992. Soil quality: attributes and relationship to alternative and sustainable agriculture. Am. J. Alternative Agric. 7, 5–11. Protz, R., Shipitalo, M.J., Mermut, A.R., Fax, C.A., 1987. Image analyses of soils—present and future. Geoderma 40, 115–125. Qian, P., Schoenau, J.J., Huang, W.Z., 1992. Use of ion exchange membranes in routing soil testing. Commun. Soil Sci. Plant Anal. 23, 1791–1804. Reicosky, D.C., Kemper, W.D., Langdale, G.W., Douglas Jr., C.L., Rasmussen, P.E., 1995. Soil organic matter changes resulting from tillage and biomass production. J. Soil Water Cons. 50, 253–262. Sanchez, P.A., Buol, S.W., 1975. Soils of tropics and the world food crisis. Science 188, 598–603. Sanchez, P.A., Buresh, R.J., Leakey, R.R.B., 1997. Trees. In: Greenland, D.J., Gregory, P.J., Nye, P.H. ŽEds.., Soils and Food Security. Land Resources: On The Edge of Malthusian Precipice? CAB International, London, pp. 89–101. Sawhney, B.L., Brown, K. ŽEds.., 1989. Reaction and Movement of Organic Chemicals in Soils. Soil Science Society of America, Madison, WI, Special Issue, No. 22. Schroeder, P., 1993. Agroforestry systems: integrated land use to store and conserve carbon. Clim. Res. 3, 53–60. Simonson, R.W., 1991. Soil science—goals for the next 75 years. Soil Sci. 151, 7–18. Sims, J.T., 2000. Soil fertility evolution. In: Sumner, M.E. ŽEd.., Handbook of Soil Science. CRC Press, Boca Raton, pp. D-113–D-153. Singer, M.J., Ewing, S., 2000. Soil quality. In: Sumner, M.E. ŽEd.., Handbook of Soil Science. CRC Press, Boca Raton, pp. G-271–G-298.

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

425

Skipper, H.D, Turco, R.F ŽEds.., 1995. Bioremediation: science and application. Soil Science Society of America, Madison WI, Special Publ. No. 43. Smart, P., Tovey, N.K., 1982. Electron Microscopy of Soils and Sediments—Techniques. Oxford Univ. Press, Oxford. Smith, J.L., Halvorson, J.J., Papendick, R.I., 1994. Multiple variable indicator kriging: a procedure for integrating soil quality indicators. In: Doran, J.W., Coleman, D.C., Bezdicek, D.F., Stewart, B.A. ŽEds.., Defining Soil Quality for Sustainable Environment. Soil Science Society of America, Madison, WI, pp. 149–157, Special Publ. No. 35. Soil Survey Staff, 1975. Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys. 2nd edn. USDA-SCS Agric. Handb., vol. 436, U.S. Govt. Print. Office, Washington, DC. Soil Survey Staff, 1999. Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys. USDA-SCS Agric. Handb., vol. 436, U.S. Govt. Print. Office, Washington, DC. Sombroek, W.G., 1984. Towards a global soil resource inventory at a scale 1:1 M. Working paper and reprint 84r4, ISRIC. Spaargaren, O.C., 2000. Other systems of soil classification. In: Sumner, M.E. ŽEd.., Handbook of Soil Science. CRC Press, Boca Raton, pp. E-137–E-174. Sparks, D.L., 1988. Soil Physical Chemistry. CRC Press, Boca Raton, FL. Sparks, D.L., 2000. Soil chemistry: past achievement and new frontiers. In: Kheoruenromne, I., Theerawong, S. ŽEds.., Soil Science: Accomplishments and Changing Paradigm Towards the 21st century. Proceedings of the Int. Symp. on Soil Science; Accomplishment and Changing Paradigm Towards the 21st Century, 17–18 April, 2000, Bangkok, Thailand, The Soil and Fertilizers Society of Thailand, pp. 15–28. Stoops, G., Dalvigne, J., 1990. Morphology of mineral weathering and neoformation. II Neoformations. In: Douglas, L.A. ŽEd.., Soil Micromorphology: A Basic and Applied Science. Proceedings of the 8th Inter. Working Meting on Soil Micromorphology, San Antonio, TX, July 1988, Elsevier, Amsterdam, pp. 483–500. Stoorvogel, J.J., Smaling, E.M.A., 1990. Assessment of soil nutrition depletion in Sub-Saharan Africa: 1983–2000. Report No. 28. Winand Staring Centre, Wageningen, The Netherlands. TAC, 1993. Ecoregional approach to research in the CGIAR; report of the TACrCenter directors working group. Technical Advisory Committee ŽTAC. Secretariat, FAO, Rome. UNEP, 1997. In: Middleton, N., Thomas, D. ŽEds.., World Atlas of Desertification. 2nd edn. UNEP, New York. United Nations Conference on Environment and Development ŽUNCED., 1992. United Nations Conference on Environment and Development. Rio de Janeiro, Brazil. United States Department of Energy, 1999. Carbon sequestration, state of the science. A working paper for roadmapping future carbon sequestration Research and Development. U.S. Department of Energy Office of Science, Office of Fossil Fuel, Washington, DC. Unruh, J.D., Houghton, R.A., Lefebvre, P.A., 1993. Carbon storage in agroforestry: an estimate for Sub-Saharan Africa. Clim. Res. 3, 39–52. van Baren, H.J.V., Hartemink, A.E., Tinker, P.B., 2000. 75 years of the International Society of Soil Science. Geoderma 96, 1–18. van Engelen, V.W.P., 2000. SOTER: the world soils and terrain database. In: Sumner, M.E. ŽEd.., Handbook of Soil Science. CRC Press, Boca Raton, pp. H-19–H-28. Viscarra, R.A., McBratney, A.B., 1998. Laboratory evaluation of proximal sensing technique for simultaneous measurement of soil clay and water content. Geoderma 85, 19–39. Webster, R., 1994. The development of pedometrics. Geoderma 62, 1–15. Wild, A., 1994. Soils and Environment, An Introduction. Cambridge Univ. Press, UK. Winterbottom, R., Hazelwood, P.T., 1987. Agroforestry and sustainable development: making the connection. Ambio 16, 100–110.

426

A.R. Mermut, H. Eswaranr Geoderma 100 (2001) 403–426

World Commission on Environment and Development, 1987. Our common future. WCED, Oxford, Oxford Univ. Press, Oxford, UK. Yaalon, D.H., 1999. On the importance of international communication in soil science. Eurasian Soil Sci. 32, 3032. Yaalon, D.H., 2000. Down to earth, why soil—and soil science—matters. Nature 407, p. 301. Yaalon, D.H., Arnold, R.W., 2000. Attitudes towards soils and their societal relevance: then and now. Soil Sci. 165, 5–12. Young, A., 1998. Land Resources, Now and The Future. Cambridge Univ. Press, New York, USA.