Burlington Northern (Somers), MT

Land treatment


leakage of underground storage tanks or are added directly to agricultural soils as the "inactive" ingredients of pesticides. Many pesticide formulations contain 7-14% BTEX by weight as carriers. Benzene in particular is a known carcinogen and is soluble in water at concentrations far greater than the drinking water standard (1 ^g liter-1). For BTEX compounds, the principal concern is their ready migration away from source areas.

Polycyclic aromatic hydrocarbons are the contaminants of concern at manufacturing petroleum plants and EPA Superfund sites across the United States (Table 17.9). Of the PAHs, the high-molecular-weight compounds (those with four or more rings) are of most concern with respect to health risks since a number of these compounds are known carcinogens. PAHs in general are characterized by very low solubility in water.

In addition, these compounds readily form nonaqueous phases in soil and sediment and also bind tightly to soil constituents such as SOM. Despite the limited water solubility of PAHs, PAH-contaminated sediment can lead to teratogenicity and toxicity of the water. Contaminated sediments represent a continuing source of contamination in the aquatic food chain.

Despite the high potential for bioremediation as an effective technology, its use is limited by the depth of understanding of biodegradation processes and inexperience in managing these processes in the field. This includes aspects of cometab-olism, inoculation, evolution of biodegradation capabilities, monitoring and process control, measures of effectiveness, and genetic engineering.

concluding comments on microbial ecology

From the foregoing discussion it is evident that humans can and have managed microorganisms for our own benefit. However, much of our discussion has centered on "unnatural" systems in which we manipulate the organism environment to accomplish the desired outcome. For example, culturing all of the organisms in a gram of soil and using them in a fermentation of grape juice would produce undrinkable wine, but inoculating the fermentation with specific species of microorganisms produces a quality product. In composting for gardens or commercial production, the operation is usually controlled at least with respect to ingredients, aeration, and moisture.

But what are the options and benefits with organisms and their management in "natural" environments? In natural environments, the mass of organisms and species composition (structure) are governed by the environment, including habitat, moisture, and temperature. Organisms form trophic levels with various modes of interaction and coexistence, from symbiotic to predatory. The community of soil organisms may increase or decrease and their composition may change principally due to influences of abiotic microclimate and natural input of metaboli-cally available substrates (plant litter, leachates, and exudates). The complexity of the system dictates that introduced organisms must find a niche to survive and be persistent. In general, organisms introduced into a soil system do not usually survive more than a period of days to weeks. The reason for poor survival rates could be due to nutrient competition, susceptibility to predation and chemical attack due to differences in cell chemistry from culturing, or simply nutrient deficiencies.

In natural systems, organisms can be structured compartmentally to be close to other organism for symbiosis, away from other organisms for protection, and in proximity to nutrients and water. An example of organism symbiosis is fungi breaking down the macromolecule cellulose into smaller more "digestible" compounds that can be utilized by other bacteria and fungi that cannot utilize cellulose directly. In addition, an organism may need a specific growth factor or vitamin that may be produced by specific bacteria, thus by growing in a mixed culture (soil) the first organism receives "nutritional symbiosis." There is, however, a down side to living among a myriad of different organisms, that is, some are predators and some will resort to predation to survive. Predation is probably the biggest factor in organism composition changes over time. When carbon inputs from litter reach the soil, bacteria increase in numbers, and then bacterial-feeding protozoa increase and a new short equilibrium will be reached in community composition. This cyclic flux in population structure drives the complex food web system of the soil and dictates nutrient availability to plants. From this perspective, perhaps it is the soil microflora who is doing the "managing" in many ecosystems.

references and suggested reading

Aislabie, J. M., Richards, N. K., and Boul, H. L. (1997). Microbial degradation of DDT and its residues—a review. N. Z. J. Agric. Res. 40, 269-282. Alexander, M. (1994). "Biodegradation and Bioremediation." Academic Press, New York. Anonymous (2003). "Bioremediation of Metals and Radionuclides: a NABIR Primer." 2nd ed. Lawrence Berkeley National Laboratory, U.S. Department of Energy Publication LBNL-42595.

Arshad, M., and Frankenberger, W. T. (1998). Plant growth-regulating substances in the rhizosphere: microbial production and functions. Adv. Agron. 62, 46—125.

Bailey, V. L., Smith, J. L., and Bolton, H., Jr. (2002). Fungal-to-bacterial ratios in soils investigated for enhanced C sequestration. Soil Biol. Biochem. 34, 997-1007.

Bauer, A., and Black A. L. (1981). Soil carbon, nitrogen and bulk density comparisons in two cropland tillage systems after 2 years and in virgin grassland. Soil Sci. Soc. Am. J. 45, 1166-1170.

Bowden, G. D., and Rovira, A. D. (1999). The rhizosphere and its management to improve plant growth. Adv. Agron. 66, 2-76.

Bumpus, J. A., and Aust, S. D. (1987). Biodegradation of DDT [1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane] by the white rot fungus Phanerochaete chrysosporium. Appl. Environ. Microbiol. 53, 2001-2008.

Calderon, F. J., Jackson, L. E., Scow, K. M., and Rolston, D. E. (2000). Microbial responses to simulated tillage in cultivated and uncultivated soils. Soil Biol. Biochem. 32, 1547-1559.

Campbell, C. A., Nicholaichuk, W., and Warder, F. G. (1975). Effects of a wheat-summer-fallow rotation on subsoil nitrate. Can. J. Soil. Sci. 55, 279-286.

Campbell, C. A., Paul, E. A., and McGill, W. B. (1976). Effect of cultivation and cropping on the amounts and forms of soil N. In "Western Canadian Nitrogen Symposium Proceedings" pp. 7-101. Calgary, Alberta.

Clark, M. S., Horwath, W. R., Shennan, C., and Scow, K. M. (1998). Changes in soil chemical properties resulting from organic and low-input farming practices. Soil Sci. Soc. Am. J. 90, 662-671.

Cooperband, L. (2002). "The Art and Science of Composting." Univ. of Wisconsin Press, Madison.

Curci, M., Pizzigallo, M. D. R., Crecchio, C., and Mininni, R. (1997). Effects of conventional tillage on biochemical properties of soils. Biol. Fertil. Soils 25, 1-6.

Dalal, R. C., and Mayer, R. J. (1986). Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. II. Total organic carbon and its rate of loss from the soil profile. Aust. J. Soil Res. 24, 281-292.

Dalal, R. C., Henderson, P. A., and Glasby, J. M. (1991). Organic matter and microbial biomass after 20 years of zero-tillage. Soil Biol. Biochem. 5, 435-441.

Diaz, L. F., Savage, G. M., Eggerth, L. L., and Golueke, C. G. (1993). "Composting and recycling municipal solid waste." Lewis Publishers, Boca Raton, Florida.

Doran, J. W. (1980). Soil microbial and biochemical changes associated with reduced tillage. Soil Sci. Soc. Am. J. 44, 765-771.

Doran, J. W., and Parkin, T. B. (1996). Quantitative indicators of soil quality: a minimum data set. In "Methods for Assessing Soil Quality" (J. W. Doran and A. J. Jones, eds.), Special Publication 49, pp. 25-38. Soil Sci. Soc. Am., Madison, WI.

Doughty, J. L., Cook, F. D., and Warder, F. G. (1954). Effect of cultivation on the organic matter and nitrogen of brown soils. Can. J. Agric. Sci. 34, 406-410.

Forester, E. (1998). "Louis Pasteur." Johns Hopkins Univ. Press, Baltimore.

Gamliel, A., Grinsten, A., Zilberg, V., Beniches, M., Ucko, O., and Katan, J. (2000). Control of soil-borne diseases by combining soil solarization and fumigants. Acta Hortic. 71, 157-164.

Hillel, D. J. (1992). "Out of the Earth: Civilization and the Life of The Soil." Univ. of California Press, Berkeley.

Katan, J., and DeVay, J. E. (1991). "Soil Solarization." CRC Press, Boston.

Koepf, H. H., Pettersson, B. D., and Schaumann, W. (1976). "Bio-dynamic agriculture: an introduction." Anthroposophic Press, Spring Valley, New York.

Lampkin, N., and Measures, M. (2001). "Organic Farming Management Handbook." Univ. of Wales Press, Aberystwyth.

McGill, W. B., Cannon, K. R., Robertson, J. A., and Cook, F. D. (1986). Dynamics of soil microbial biomass and water soluble organic C in Breton L after 50 years of cropping to two rotations. Can. J. Soil Sci. 66, 1-19.

Oelhaf, R. C. (1978). "Organic Agriculture." Wiley, New York.

Phelps, C. D., and Young, L. Y. (2000). Biodegradation of BTEX under anaerobic conditions: a review. Adv. Agron. 70, 330-359.

Postma, J., and van Veen, J. A. (1990). Habitable pore space and survival of Rhizobium leguminosarum biovar trifolii introduced into soil. Microb. Ecol. 19, 149-161.

Purser, J. E. (1977). "The Winemakers of the Pacific Northwest." Harbor House, Vashon Island, WA.

Ramsay, C., Haglund, B., and Santo, G. (1992). "Bulletin 21: Soil Fumigation." Washington State Univ. Press, Pullman.

Rees, R. M., Ball, B. C., Campbell, C. D., and Watson, C. A. (2001). "Sustainable Management of Soil Organic Matter." CAB International, Wallingford, UK.

Reganold, J. P., Palmer, A. S., Lockhart, J. C., and Macgregor, A. N. (1993). Soil quality and financial performance of biodynamic and conventional farms in New Zealand. Science 269, 344-349.

Robertson, G. P., Paul, E. A., and Harwood, R. R. (2000). Greenhouse gases in intensive agriculture: contributions of individual gases to the radiative forcing of the atmosphere. Science 289, 1922-1925.

Rynk, R. (1992). "On-Farm Composting Handbook." NRAES Cooperative Extension, Ithaca, NY.

Sattler, F., and Wistinghauser, E. (1992). "Bio-Dynamic Farming Practice." Bio-dynamic Agric. Assoc., West Midlands, UK.

Smith, J. H. (1995). "Cheesemaking in Scotland—a History." Scottish Dairy Assoc., Glasgow.

Smith, J. L. (1994). Cycling of nitrogen through microbial activity. In "Soil Biology: Effects on Soil Quality" (J. L. Hatfield and B. A. Stewart, eds.), pp. 91-120. CRC Press, Boca Raton, FL.

Smith, J. L., and Elliot, L. F. (1990). Tillage and residue management effects on soil organic matter dynamics in semi-arid regions. In "Dryland Agriculture: Strategies for Sustainability" (B. A. Stewart, ed.), Vol. 13, pp. 69-88. Springer-Verlag, New York.

Smith, J. L., and Paul, E. A. (1990). The significance of soil microbial biomass estimations. In "Soil Biochemistry" (G. M. Bollag and G. Stotzkey, eds.), Vol. 6, pp. 357-396. Dekker, New York.

Smith, J. L., Papendick, R. I., Bezdicek, D. F., and Lynch, J. M. (1992). Soil organic matter dynamics and crop residue management. In "Soil Microbial Ecology" (B. Metting, ed.), pp. 65-94. Dekker, New York.

Staben, M. L., Bezdicek, D. F., Smith, J. L., and Fauci, M. F. (1997). Microbiological assessment of soil quality in conservation reserve program and wheat-fallow soil. Soil Sci. Soc. Am. J. 61, 124-130.

TeBeest, D. O. (1996). Biological control of weeds with plant pathogens and microbial pesticides. Adv. Agron. 56, 115-135.

Triplett, G. B. Jr., and Mannering, J. V. (1978). Crop residue management in crop rotation and multiple cropping systems. In "Crop Residue Management Systems" (W. R. Oschwald, ed.) Special Publication 31, pp. 198-206. Am. Soc. Agron., Madison, Wisconsin.

U.S. Environmental Protection Agency (1996). "A Citizen's Guide to Bioremediation." Solid Waste and Emergency Response, Technology Innovation Office, Technology Fact Sheet EPA 542-F-96-007.

Vidali, M. (2001). Bioremediation: an overview. Pure Appl. Chem. 73, 1163-1172.

Voroney, R. P., and Schuman, G. E. (1981). Organic C dynamics in grassland soils. II. Model validation and simulation of the long-term effects of cultivation and rainfall erosion. Can. J. Soil Sci. 61, 211-224.

Walker, J. C. (1950). "Plant Pathology." McGraw-Hill, New York.

Wander, M. M., Traina, S. J., Stinner, B. R., and Peters, S. E. (1994). Organic and conventional management effects on biologically active soil organic matter pools. Soil Sci. Soc. Am. J. 58, 1130-1139.

Wander, M. M., and Traina, S. J. (1996). Organic matter fractions from organic and conventional managed soils. I. Carbon and nitrogen distribution. Soil Sci. Soc. Am. J. 60, 1081-1087.

Wardle, D. A. (1995). Impacts of disturbance on detritus food webs in agro-ecosystems of contrasting tillage and weed management practices. Adv. Ecol. Res. 26, 105-182.

Wilson, D. (1976). "In Search of Penicillin." Random House, New York.

Whipps, J. M. (2001). Microbial interactions and biocontrol in the rhizosphere. J. Exp. Bot. 52, 487-511.

Organic Gardeners Composting

Organic Gardeners Composting

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