Submitted to: Biodiversity of Soil International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/17/2002
Publication Date: 3/26/2003
Citation: Pachepsky, Y.A., Young, I.M., Crawford, J.W., David, U.C., Baveye, P. 2003. How does the physics of the soil system dictate dispersal of waste-borne microorganism in soils?. Biodiversity of Soil International Conference Proceedings. p.27. Interpretive Summary:
Technical Abstract: Over the past 5 years waste disposal to soil has doubled, following the end of dumping to sea. A significant proportion of this waste will be applied to agricultural soils in the form of animal by-products and general agricultural and food-industry waste. The potential of waste-borne pathogens to disperse through soil and into watercourses is an important concern. The objective of this presentation is to summarize and stimulate research based on hypothesis that soil pore structure, and its influence on hydraulic and biological properties, control the dispersal of bacteria from wet waste applied to land. Qualitatively, it is known that a wide range of soil conditions impacts the movement of microorganisms through soil. The physical structure and composition of the soil acts as habitat, transport conduit and water reservoir of all soil organisms, and thus plays a pivotal role in the spread of micro-organisms through the ecosystem. It has been demonstrated that the spread of bacteria depends in part on the soil's pore-size distribution, adhesion forces between bacteria and soil pore surfaces, and the flow of water into the soil. Where there is little movement of the microbes with leaching water, microbes remain associated with the soil and that any movement is due to erosion under surface flow conditions. Most promising current research efforts focus on the fundamental mechanisms controlling the infiltration and movement of bacteria from waste through the soil profile, at large (m) and small (mkm - mm) scales, within a realistic theoretical framework. We show that an explicit account of the physics and biology of bacterial movement is possible if the latest molecular, mathematical and physical techniques to identify and monitor the movement of bacterial populations in soil are used. This multidisciplinary approach accommodates the fact that substrate addition to soils, especially in the large quantities involved with waste disposal, will modulate both the transport and survival properties of introduced bacteria. That leads to the development of a generic model that is transportable to many soils and does not suffer from the heavy calibration associated with some models.