Survival of biocontrol Pseudomonas fluorescens CHA0 in lysimeter effluent water depends; on time of the year and soil type

Aims: To assess the effects of soil type and time of the year on survival o f the biocontrol inoculant Pseudomonas fluorescens CHA0 under aerobic condi tions in lysimeter effluent water. Methods and Results: Effluent water was collected at different times from l arge outdoor lysimeters (2.5 m deep), which contained a well-drained or a p oorly-drained cambisol, and inoculated with CHA0. The inoculant was monitor ed for 175 d by colony counts, total immunofluorescence cell counts and Kog ure's viable cell counts. Cell numbers obtained with the three methods were similar. The inoculant declined exponentially in time and its population l evel varied considerably depending on the time of the year at which effluen t water had been collected and soil type in the lysimeter. Positive correla tions were found between the number of resident culturable aerobic bacteria and subsequent survival of the inoculant. Conclusions: The fluctuations of inoculant survival patterns correlated wit h differences in biological properties of lysimeter water that were related to soil type and time of the year. Significance and Impact of the Study: Results suggest that predictability o f the survival of bacterial soil inoculants transported to groundwater leve l by heavy rainfall may be improved by taking into account key biological p roperties of the water.