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Fig. 2. Effect of fluctuating water contents on populations of naturally occurring Escherichia coli O157, generic E. coli, and total coliforms in feedlot soils containing 25% manure. The pans were filled with three different masses of soils to attain high, intermediate, and low moisture flux ranges. Appropriate volumes of deionized distilled H2O were added weekly to return the soils to the initial water content of 0.78 g H2O g–1 of dry feedlot surface material (FSM). Where indicated by arrows, feedlot soil samples were enriched to determine the presence or absence of E. coli O157 on Days 35, 49, and 63. The three symbols at Day 35 indicate that two high moisture flux samples and one intermediate moisture flux sample were positive for E. coli O157 by enrichment. The standard errors of the least squares means were 0.21 and 0.20 for generic E. coli and total coliforms, respectively.
