## 3 Results
### Field Experiment  
Results of chemical analyses of pre-sowing, untreated, and treated soil samples collected at DS (Development Stage [37]) 49, are shown in Table 2.  
Among the different parameters analyzed, the initial soil pH--before sowing--(PS) recorded a slight decrease (\(p<0.05\); \(n=3\)) in the presence of the bacterial inoculation (SIB), while for the control no significant changes were recorded (\(p>0.05\); \(n=3\)). Concerning the pre-sowing soil sample, SIB recorded significant increases of total N, total organic C and organic matter (\(p<0.01\); \(n=3\)), while the control recorded significant decreases of the same parameters (\(p<0.01\); \(n=3\)). Moreover, the bacterial presence in SIB was able to decrease electrical conductivity (\(p<0.01\); \(n=3\)) and to positively influence soil \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Bacteria** & **Trp** & **IAC** & **IAM** \\  & **nmol (mg dry wt cells)\({}^{-1}\)** & **nmol (mg dry wt cells)\({}^{-1}\)** & **nmol (mg dry wt cells)\({}^{-1}\)** \\ \hline A\_C & 2.23 f & 0.93 de & - \\ A\_T & 1.05 hi & 0.50 fg & \textless{LOQ/LOD} \\ B\_C & 0.44 j\textasci{-}m & 0.40 gh & - \\ B\_T & 0.80 j & 0.29 h & - \\ G\_C & 1.20 g\textasci{-}h & \textless{LOQ} & - \\ G\_T & 4.30 d & 0.82 e & \\ H\_C & 3.68 e & 8.10 a & - \\ H\_T & Nq & Nq & Nq \\
4B\_C & 0.52 j\textasci{-}l & 0.37 gh & 0.09 c \\
4B\_T & 4.86 c & 1.02 cd & - \\ A+G\_C & 0.05 mm & 0.32 h & - \\ A+G\_T & 12.97 b & 2.04 b & - \\ A+B\_C & - & - & - \\ A+B\_T & 18.02 a & - & 2.66 a \\ A+H\_C & - & 0.10 i & - \\ A+H\_T & 0.59 jk & 0.62 f & 0.91 b \\ B+G\_C & 0.22 k\textasci{-}n & \textless{LOQ} & \\ B+G\_T & 2.16 f & 0.33 h & 0.10 c \\ B+H\_C & 1.50 g & 1.10 c & - \\ B+H\_T & 0.13 l\textasci{-}n & 0.33 h & - \\ G+H\_C & - & - & - \\ G+H\_T & - & - & 0.06 c \\ _F-test_ & * & ** & ** \\ LSD & 0.40 & 0.15 & 0.16 \\ \hline \hline \end{tabular}  
* In the table: A, _A. brasilense_; B, _B. ambifaria_; G, _G. diazotrophicus_; H, _H. seropedic_; C, broth culture without Tryptophan; T, broth culture added with Tryptophan; LOQ = limit of quantification; LOD, limit of detection; Nq, not quantifiable, the production was very high and overlapped with other peaks. Error bars are standard error of the means. Results followed by different letters are significantly different according to [PERSON]’s LSD test (\(p<0.05\)) following one-way ANOVA.
* \(p<0.05\); *  
\end{table} 
Table 1: Trp, IAC (indole-3-acetaldehyde) and IAM (indole-3-acetamide) concentrations detected in single strains and combined strains broth cultures with and without Trp addition by HPLC-FL. nutrients. In comparison to pre-sowing soil, Na+ and K+ showed a decrease (\(p<0.01\); \(n=3\)) and Ca2+ and Mg2+ concentrations were statistically similar (\(p>0.05\); \(n=3\)). Best concentrations of available \(p\) were recorded for SIB (\(p<0.01\)). For the control soil, except for Na+ (statistically similar to PS, \(p>0.05\); \(n=3\)), lower concentrations of all nutrients were recorded than PS and SIB soils (\(p<0.01\); \(n=3\)). The ecological indexes calculated on soil community level physiological profiles are shown in Table 3. Bacterial inoculum positively affected soil microbial communities' physiological profile, improving the overall carbon source metabolic activity of soil. The SIB AWCD (average well color development, index of carbon source utilization) and \(H\) (diversity) indexes, determined at DS 49, were significantly higher than the control ones (\(p<0.05\); \(n=3\)), while for the R index (richness), no significant differences were shown. In Table 3 the diversity indexes calculated on NGS results are shown. Calculated diversity indexes are in line with findings obtained for CLPP analysis. For the SIB condition, Diversity and Richness values were higher than the control. Figure 4 reports the relative abundances of common genera found in control and SIB samples.