ISSN:0038-075X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Although the 1900s have been an extremely productive century for soil science, the discipline got its start a century earlier when Malthus challenged the scientific world with his prediction that population growth would outstrip the world's ability to supply food. Soil science is now in a transitory phase, with tensions between production and environmental protection and between the more basic and the applied sciences. In the future, soil scientists will have to be involved both in feeding the world and in helping society.

ISSN:0038-075X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Soils are relevant to society in diverse ways, supplying various economic and cultural services or functions as well as being the substrate for plants and a life-support system. Attitudes to the diverse kinds of soil resources and resulting land-use practices throughout human history indicate that mankind has frequently used other than the most fertile or easiest accessible soils. Many special techniques, such as terracing, have been developed to utilize and preserve less accessible land and shallow soil on slopes. Soil degradation and erosion following deforestation have frequently been a problem in the past, especially when some land was abandoned for cultural or economic reasons. Better data on current degree and extent of soil degradation are needed.Man has made soils fertile on a large scale, providing more secure food resources for the ever growing population. Yet, there is a growing threat to soils, in many instances, on marginal soils or in less resilient soil regions. A good environmental ethic requires equally good soil care of open spaces and of forests, woods, and deserts for better quality of life and for future generations of town and country populations. For this purpose an Eleventh Commandment was formulated a generation ago, and efforts are now being made to institute an internationally secured global treaty or soil convention for better soil care and sustainable use of soils. Soil scientists need to support such proposals and to bridge the gaps and differences between local and governmental efforts.

ISSN:0038-075X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The thin layer of soil on the earth's surface performs many functions essential to life. Humankind has known of the importance of this resource for thousands of years, but formal study of soils began only in the 1800s using knowledge acquired in the basic sciences of physics, chemistry, and biology. During the mid-1800s, much of the infrastructure for soil science was put into place. Land-grant universities and experiment stations were established, and funding mechanisms for conducting research were created. In the early 1900s, as the number of scientists grew and the level of research activity increased, professional societies were formed, and scholarly journals began publication. Research efforts during this time concentrated on understanding water movement and nutrient availability largely as it applied to crop production. As a consequence of natural and human aggravated disasters, such as the American dust bowl in the 1930s, management practices were developed to reduce wind and water erosion and conserve the soil resource. In the 1960s, environmental awareness grew, and research efforts were directed at understanding the processes involved in environmental contamination, development of management practices to reduce the potential for environmental contamination, and procedures to remediate contaminated sites. Soils research has accomplished much, providing us with a thorough understanding of the physical, chemical, and biological properties and processes of soils, determining the role of soils in environmental quality, and developing the management practices used to produce a bountiful food supply. However, despite these accomplishments and continued demands for soils-related information, soil scientists are currently facing many challenges. A steady supply of inexpensive, high quality food produced by less than 2% of a largely urban population has left the majority of people with little appreciation of the problems and challenges facing agriculture. Competing interests for budget dollars have left funding for agricultural research level or in decline in recent years. In addition, the current crisis in agriculture has resulted in a lower market share than ever before being returned to farmers, leaving producers with little incentive or flexibility to change management practices. Soil scientists must work with these challenges to ensure that the science is available to address critical problems facing society, namely: population pressure and the need for increasing agricultural productivity; competing uses for land and water resources; dependence on nonrenewable resources; and environmental quality, especially in developing countries. Facing current challenges and solving future problems will likely require that soil scientists conduct research differently than in the past, with greater emphasis on holistic team- and interdisciplinary analyses of problem areas, followed by reductionist disciplinary research that ensures optimal use of research resources.

ISSN:0038-075X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Although urban and suburban soils are used for many purposes, some of them relevant to agricultural and forest sciences, that these intensively managed and disturbed soils have not been extensively investigated up to now is suggested by the white areas representing most urban zones on soil survey maps. Because urban soils are often developed on composite materials derived from previous uses and exogenous sources, spatial heterogeneity is a typical feature. Their evolution is controlled almost exclusively by humans, who impose very rapid transformation cycles compared with those occurring in less disturbed areas. However, there is a continuum from the natural soils to the extensively disturbed soils, and their basic functions are essentially the same. As a result of their origin and uses, urban soils may contain pollutants, the location, characteristics, and potential evolution of which must be established clearly to ensure safe land uses. These soils can be investigated with the traditional soil survey approach when the techniques are adapted properly to the urban context. A multidisciplinary approach is necessary to ensure that urban soils are well understood in order to ensure their optimum use.

ISSN:0038-075X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

During the golden era of soil science-from the 1950s to the 1980s-the main focus of this discipline was on the role of soil in production agriculture. More recently, renewed interest in the area of environmental science has offered new opportunities to soil scientists. Thus, many soil scientists are now working in areas such as bioremediation, waste recycling, and/or contaminant transport. Environmental science has, therefore, not only changed the traditional research role of soil scientists at land grant institutions but has also influenced student enrollment, the traditional soil science curriculum, and faculty recruitment. These changes require a new breed of soil scientist, one with a background not only in soil science but also in other areas of environmental science as well.

ISSN:0038-075X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

In the interplay of the soil and the atmosphere, the soil can be both a contributor to and a recipient of the impacts of climate change. In the past, land management has generally resulted in considerable depletion of soil organic matter and the release into the atmosphere of such radiatively active gases as carbon dioxide, methane, and nitrous oxide. Global climate change, to the extent that it occurs, will strongly impact all soil processes. At this time, the task of soil management should be to restore soil organic carbon in order to enhance soil structure and fertility and to help counter the atmospheric greenhouse effect. Widely varying estimates of the soil's organic carbon content and of the potential for soil carbon sequestration point to the need to conduct a comprehensive inventory of this important property.

ISSN:0038-075X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The present world population of 6 billion will reach 8 billion by 2020 and 9.4 billion by 2050. By then, the population will have increased by another 575 million in India, 300 million in China, 200 million in Nigeria, 200 million in Pakistan, and 140 million in Ethiopia. Of the total world population, 8.2 billion will live in developing countries, of which 3 billion will reside in arid and semiarid environments. Thus, soil management challenges for developing countries include achieving food security with minimal risks to environment given per capita land area decreasing to <0.1 ha and per capita irrigated land area to <0.04 ha, severe scarcity of renewable fresh water resources, high risks of soil degradation by a wide range of degradative processes, resource-poor farmers, and weak institutional support. Productivity loss attributable to erosion-caused soil degradation is estimated at 18 million Mg of food staples per year at the 1990 level of yields for subSaharan Africa and 272 million Mg for the world at the 1996 level of production. The productivity loss at a landscape level may range from 0 (or even positive effect) to total crop failure. In addition to enhancing productivity per unit area and per unit time, soil management technologies must also address pressing environmental issues, especially with regard to the greenhouse effect and air quality, water quality, and land application of industrial and urban wastes. Enhancing food production would necessitate adoption of land saving technologies through agricultural intensification on prime agricultural land, conversion of marginal lands to other appropriate land uses, and restoration of degraded lands and ecosystems. Soil-specific technologies for agricultural intensification will have to be developed, fine-tuned, and adopted. These technologies will address the issue of: (i) enhancing soil structure, (ii) increasing nutrient use efficiency through integrated nutrient management and strengthening nutrient recycling mechanisms, (iii) conserving soil and water through residue management and adoption of conservation tillage, (iv) improving water use efficiency through development and adoption of efficient methods of water harvesting, recycling and irrigation, and (v) increasing cropping intensity. Improvements in rainfed agriculture through water conservation and enhancing water and nutrient use efficiencies will be a major challenge in subSaharan Africa, India, Central Asian countries, northeastern Brazil, and other semiarid regions of the developing world. Preventing and restoring degraded soils, enhancing soil C sequestration to mitigate the greenhouse effect, and decreasing risks of eutrophication of surface water and contamination of ground water will be priority issues. Soil scientists will need to work closely with those in the basic sciences to address the environmental concerns of agricultural intensification. There is a strong need for high quality, credible, innovative, original, and demand-driven research in soil science in developing countries. Research managers can facilitate achievements of goals of high quality science by creating a conducive and trustworthy work atmosphere and by rewarding productivity and merit.

ISSN:0038-075X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Soil Science integrates specific contributions from physics, chemistry, biology, and the human sciences. During the last 2 decades, these approaches, which had primarily developed separately and at different speeds, have been progressively integrated. Ecology has contributed a significant number of integrative concepts and questions, some, such as nutrient cycling and energy budgets, that are rather old, and others, such as soil engineering by macroinvertebrates, the relationship between biodiversity and soil function, and the impact of landscape fractionation, that are more recent.An important issue common to all disciplines in Soil Science is that of scales. Ecological studies have shown that similar activities, e.g., the building of solid structures by invertebrates for their sheltering or gut transit of soil for digestion, may affect soil function at different scales, affecting the rates of processes in sometimes opposite directions. The concept of functional domains in soil, derived from soil ecological research, defines a scale at which physical, chemical, and biological processes can be studied efficiently in a true multidisciplinary approach. Functional domains are specific sites in soils defined by a main organic resource (leaf litter or soil organic matter), a major regulator, biotic (i.e., an invertebrate 'engineer' or roots) or abiotic (like freezing/ thawing or drying/rewetting alternates), a set of structures created by the regulator (for example, fecal pellets, galleries, or cracks), and a community of dependent invertebrates of smaller size and microorganisms that live in these structures. Functional domains may be physically identified in soils and specifically studied using the different disciplinary approaches. Specific micromorphologic, isotopic, and other techniques allow us to address issues at this scale adequately. Ecological research also provides a theoretical background for management of soils at the larger integrative scales of landscape and regions.Essential issues for the near future should use this interdisciplinary approach. Sustainability of cropping systems and maintenance of soil ecosystem services depend more on an integrated approach than do the extreme developments in single disciplines in isolation that originated the series of problems we now face: large scale soil erosion, nutrient transfers to neighboring ecosystems, threats of genetically modified organisms, or biodiversity accidents.

ISSN:0038-075X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

National well-being will continue to depend on the productive use of soils, but society will increasingly demand that soils be managed sustainably. Soil scientists, therefore, need to contribute technology to land management in a holistic way to satisfy society's requirements. They must also help formulate public policy, contribute to public understanding of environmental issues, and be alert to opportunities provided by new knowledge to improve soil and land management. Close cooperation with land owners and managers is necessary. Appropriate training of soil scientists is needed to prepare them for these responsibilities. Training in the natural sciences is a prerequisite for both vocational and research careers in soil science. This basic training should be concurrent with, or followed by, adequate exposure to the principal subdisciplines of soil science. Training in team-based problem solving is essential. Examples that support these assertions are discussed.

ISSN:0038-075X    

出版商:OVID    

年代:2000

数据来源: OVID