Results
Overall plant growth was increased by an average of 43.3% when inoculated with microorganisms (p = 0.0001, CI = 29.69% - 58%, Figure 1A). Most studies reported positive effects of microbial inoculation on plant growth (N = 158, 92%), with only 13 of the 172 observations (7.5 %) reporting negative effects of microbial inoculation and a single record finding no statistically significant effect of inoculation on plant growth.
Native microbial inoculants increased plant growth on average by 53% (CI = 31% - 80%, replicates (N) = 78) while commercial inoculants increased plant growth by 40% (CI = 9% - 78%, replicates (N) = 23). However, we found no statistically significant difference between the two types of inoculants (p = 0.57, CI = -0.18 – 0.37, Figure 1B).
Single microbial inoculants increased plant biomass by an average of 39% (CI = 24% - 55%, replicates (N) = 108) while multiple strain inoculants (biodiverse microbes) increased plant biomass by 49% (CI = 32% - 68%, N = 64). This difference was not statistically significant (p = 0.27, CI = -16.71% – 5.12%, Figure 1C).
Fungal inoculation increased plant biomass by 39% (CI = 28% - 61%, N = 88) while bacteria inoculation increased plant biomass by 43% (CI = 23% - 58%, N = 77). We found no statistically significant difference between the effect of bacteria and the effect of fungi on plant growth (p = 0.69, CI = -15.6% - 11%, Figure 1D).