MOVEMENT OF BACTERIA IN UNSATURATED SOIL COLUMNS WITH MACROPORES

Rapid movement of bacteria through the sail has been observed after ap plications of manure to agricultural fields. Preferential flow through macropores has been suggested as the main reasons for these observati ons. Experiments with repacked soil columns were used to study the eff ect of artificially created macropores, soil type, soil water content, and simulated rain application on movement of a tracer bacterium nali dixic acid-resistant Escherichia coli. Results form these experiments showed a significant increase in the number of biotracer cells passing through a soil column when macropores were present and the soil was w et. There was no passage of biotracer cells through a dry soil with ma cropores. No biotracer cells were eluted from columns without macropor es even when the soils were wet. Simulated rainfall applied on the tap of the soil columns caused bacteria to travel deeper into the soil. T hese results confirm the important role that macropores play in the mo vement of bacteria through heterogenous soils.