Survival in two soils with the highest clay content was approximately 4 fold longer, with laboratory data mimicking the field results. When the plants were present in the microcosms, the difference between soil types was not as great. Rhizosphere microcosm data obtained from samples shipped to Maryland were identical to on site samples. In AG and BC soils, survival in the field closely paralleled microcosm survival and the microcosm served as an accurate predictive tool. Indications are that wheat plants in the field, which tend to have about ten times more above and below ground biomass than in microcosms at these sites, enhance survival of the GEM to a greater extent than plants in a microcosm.
Data indicate that there are differences in survival and persistence due to soil type and climate.
However, in all climates and with all soil types, the microcosm protocol is able to generate laboratory data which is comparable to field data. In addition, trials conducted in Maryland, with samples shipped from the four locations, indicate that off site data, generated using the microcosm protocol, is comparable to field data from any site. Presence or absence of the plant greatly affects the persistence and survival of both the GEM and parent microbe. Enumeration and Expression of Bacterial Counts in the Rhizosphere. Stotzky, G. and Bollag, J.M. eds.