Storage effects on indigenous soil microbial communities and PGPR efficacy

We tested the hypothesis that storage-induced changes in the composition of soil microbial communities altered the efficacy of three Bacillus and three Pseudomonas plant growth promoting rhizobacteria (PGPR) strains on spruce seedlings. Forest soils were collected from near Mackenzie, Salmon Arm and Williams Lake, B.C. Soil microbial population sizes were evaluated using dilution plating. Carbon substrate utilization patterns were determined on fresh forest soils and after 32 weeks of storage at 4°C and −10°C using the Biolog system. Small aliquots of fresh and stored soils comprising