We evaluated the significance of CaCO3 on survival of P. fluorescens CHA0-Rif at different temperatures. Suspensions of CHA0-Rif were added to soil mixtures at a rate of 106 cells g−1 soil. Survival was evaluated in sterile or nonsterile mixtures containing 0, 5, 10, 15, or 25% CaCO3. Mixtures were incubated at 4, 15, or 37°C. Water content was adjusted at field capacity. Each treatment was tested in triplicate. Destructive sampling was carried out to verify persistence of culturable CHA0-Rif at different time intervals. Incubation temperature (T), sterilization (S), and their interactions were significant for the decay rates of CHA0-Rif (p < 0.01). At 15°C, the longest survival was measured in the mixtures with the largest CaCO3 content. Incubation at 37°C accelerated die-off and thus obscured any possible effect of CaCO3. The maximum decay rate of 1.81 d−1 was measured in the nonsterile mixture incubated at 37°C; whereas the minimum decay rate of 0.01 d−1 was calculated for the sterile soil incubated at 4°C. Overall, P. fluorescens CHA0-Rif survival was mostly affected by temperature and competitor microorganisms. However, the presence of CaCO3 may also have a possible role by suppression of other microorganisms in favor of CHA0-Rif.
