Soil Science
Michael J. Singer

Soil science has historically been taught within colleges of agriculture, where most research was applied to improving crop yields and management of agricultural soils. Since the first Earth Day in 1970, however, many soil scientists have refocused their research to issues of environmental quality. Highlights of recent soil science research with an environmental focus are given here. For details, consider reading papers published by the Soil Science Society of America and American Society of Agronomy, including Soil Science Society of America Journal, Journal of Environmental Quality, and Vadose Zone Journal.

One heaping tablespoon of soil may contain up to 9 billion microorganisms — one and a half times the human population on Earth. Amidst this vast number and variety are a host of microbes now valued for their potential to help solve environmental problems. But soil is also home to many disease bacteria, including botulism and anthrax, and soil scientists reason that organisms in soil may supply the cure as well as the disease. This idea is not far-fetched: The only soil scientist ever to win a Nobel prize was Selman Waxman of Rutgers University, who received the Physiology and Medicine award for his discovery of the antibiotic, streptomycin, in 1952. Streptomycin was the first drug to show value in treating tuberculosis.

Environmental remediation

The application of molecular biology to soil microorganisms is opening a new world for soil microbiologists, who investigate the role of microorganisms in soil and groundwater remediation. A recent example is the discovery and culture of an organism that utilizes the gasoline additive MTBE (methyl tertiary-butyl ether) as an energy source. The organism is now being introduced into polluted groundwater on a military facility to determine the efficacy of this approach to groundwater remediation. Bioreclamation of potentially toxic organic materials such as perchlorate and chlorophenol are other examples of how soil microorganisms are put to work to remedy environmental pollution.

Phytoremediation, the use of plants to remove toxic trace elements from soils has been accelerated by the genomics and molecular biology revolution as well. Now, in addition to isolating plants that are naturally adept at concentrating metals, soil scientists and plant scientists are creating transgenic plants that are more efficient phytoremediators than naturally occurring species.

Soil scientists are also helping to transform former approaches to waste and its removal. Traditional disposal methods are giving way to new waste utilization technologies, made possible by a thorough understanding of the properties of biosolids (treated human waste). The use of biosolids in soil reclamation and remediation is now common.

One concern with biosolids utilization is their trace-metal composition. Soil scientists continue to make progress in understanding the distribution, reactivity and fate of heavy metals in the environment. Soil, because of its high surface area and reactivity, provides a critical filter that protects groundwater and surface water from heavy-metal contamination. As they investigate the properties of metallic elements such as chromium, cadmium, lead and copper, scientists are able to apply their growing knowledge to soil remediation projects in order to prevent the transfer of these and other metals to groundwater and surface water.

Surface water quality is also affected by overland flow from urban and agricultural watersheds. Soil scientists study the processes that move sediment, nitrogen, phosphorus and pathogens into surface waters. New computer models are proving useful in predicting where and when these pollutants will be transported from watersheds to receiving water bodies so that effective soil conservation practices can be implemented.

Carbon cycling and its role in global climate change is an important area of soil science research. Carbon sequestration by soils has been shown to have the potential to slow the increase in atmospheric carbon-dioxide concentration. A major advance in farming systems now being widely adopted is the use of conservation tillage, which reduces soil disturbance and increases the retention of recalcitrant carbon that would otherwise be released to the atmosphere as carbon dioxide. Soil scientists are also investigating the cycling of other greenhouse gases, including nitrogen gases and methane, in order to develop methods for reducing their production and release to the atmosphere.

Soil science research spans spatial scales from nanometer to kilometer and from basic processes to practical applications. Every facet of human life is affected by soil — from what we eat to where we live and how we dispose of waste. Soil scientists contribute to our understanding of where resources exist, their properties, functions and management. Although food production for a growing population continues to be an important theme in much soil science research, environmental research also drives the soil scientist's agenda.

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Singer is president of the Soil Science Society of America, professor of soil science and chair of the Department of Land, Air and Water Resources at the University of California-Davis. E-mail:

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