## 4 Discussion  
### Black Seeded Simpson (BSS) Trials  
For BSS1, the observed increase in shoot biomass was greatest at the slightly deficient N rate of 105 mg L\({}^{-1}\) N. At this N rate, INOC outperformed NON by 456 mg dry matter, an increase of 14.8% (Figure 2a). This corresponds to the best conservative fertilization rate, because the harvested aerial biomass was greater at this combination of _G. diaz_ and fertilization than that for all NON plants fertilized at an equivalent or higher rate. By inoculating with _G. diaz_, a grower could decrease the amount of N fertilizer use by 42.8% (150 mgL\({}^{-1}\) reduced to 105 mgL\({}^{-1}\)) for the same biomass yield, which would represent a considerable savings on the cost of fertilizer input. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multicolumn{1}{c}{} & \multicolumn{3}{c}{**Fertilizer Treatment Provided Nitrogen Concentration (ppm)**} & \\ Trial and Measure & 37.5 & 60 & 82.5 & 105 & 127.5 & 150 & 172.5 \\ BIB1 & & & & & & \\ SDM Nitrogen \% ** & n/s & & & & & \\ INOC & - & 1.078 & 1.167 & 1.525 & 1.813 & 1.853 & 2.275 \\ NON & - & 1.095 & 1.284 & 1.612 & 1.729 & 2.059 & 2.122 \\ Difference & - & \(-\)0.017 & \(-\)0.118 & \(-\)0.087 & 0.085 & \(-\)0.207 & 0.153 \\ SDM C/N Ratio ** & n/s & & & & & \\ INOC & - & 36.990 & 34.444 & 26.534 & 22.670 & 21.712 & 17.938 \\ NON & - & 36.442 & 31.337 & 25.226 & 23.529 & 19.697 & 19.051 \\ Difference & - & 0.548 & 3.107 & 1.308 & \(-\)0.860 & 2.015 & \(-\)1.114 \\ RDM Nitrogen \% & n/s & & & & & \\ INOC & - & 0.929 & 1.016 & 1.396 & 1.661 & 1.712 & 2.293 \\ NON & - & 0.961 & 1.119 & 1.265 & 1.583 & 1.693 & 2.090 \\ Difference & - & \(-\)0.031 & \(-\)0.103 & 0.131 & 0.079 & 0.018 & 0.204 \\ RDM C/N Ratio & n/s & & & & & \\ INOC & - & 38.137 & 37.768 & 29.106 & 23.449 & 22.393 & 17.555 \\ NON & - & 36.593 & 30.946 & 29.356 & 23.147 & 17.578 & 17.169 \\ Difference & - & 1.544 & 6.822 & \(-\)0.250 & 0.303 & 4.815 & 0.385 \\ BIB2 & & & & & & \\ SDM Nitrogen \% ** & LSD: \(-\)0.2767 s.e.: 0.1311 df = 29 p \(\leq\) 0.0436 & & & & \\ INOC & - & 0.821 & 0.525 & 1.347 & 1.944 & 2.578 & 2.711 \\ NON & - & 1.166 & 1.018 & 1.794 & 2.266 & 2.517 & 2.598 \\ Difference & - & \(-\)0.345 & \(-\)0.493 & \(-\)0.447 & \(-\)0.321 & 0.061 & 0.113 \\ SDM C/N Ratio ** & LSD: 4.3860 s.e.: 1.8028 df = 29 p \(\leq\) 0.0214 & & & & \\ INOC & - & 46.711 & 54.038 & 34.718 & 21.985 & 18.160 & 15.702 \\ NON & - & 45.598 & 42.960 & 24.143 & 20.420 & 16.329 & 15.546 \\ Difference & - & 1.113 & 11.078 & 10.575 & 1.565 & 1.830 & 0.155 \\ RDM Nitrogen \% & n/s & & & & & \\ INOC & - & 0.976 & 1.086 & 1.711 & 3.172 & 3.247 & 2.854 \\ NON & - & 1.602 & 1.470 & 1.926 & 2.681 & 2.901 & 2.901 \\ Difference & - & \(-\)0.627 & \(-\)0.384 & \(-\)0.215 & 0.491 & 0.346 & \(-\)0.047 \\ RDM C/N Ratio & n/s & & & & & \\ INOC & - & 37.729 & 30.613 & 25.942 & 14.957 & 16.632 & 16.155 \\ NON & - & 29.565 & 28.208 & 22.692 & 18.673 & 15.365 & 16.032 \\ Difference & - & 8.164 & 2.405 & 3.250 & \(-\)3.717 & 1.267 & 0.123 \\ \hline \hline \end{tabular}  
* = significant at alpha \(<\) 0.01, ** \(\leq\) 0.05, n/s = not significant. Note: Bolded main effect level shows which treatment was significantly greater. \({}^{\prime}\)- indicates that this fertilization (FERT) level was not used in this experiment.  
\end{table} 
Table 4: Effects of inoculation and nitrogen fertilization on the BIB/Limestone N density and C/N ratios. At the same time, the root biomass decreased by 425 mg dry weight, or 41.0% (Figure 2b), with no significant difference in total biomass accumulation in the whole plant (TDM). Inoculated plants shifted biomass synthesis away from root tissues and into shoot tissues. Since root material is of no value in hydroponic lettuce production, there is no detriment due to reduced root biomass production under hydroponic growth conditions. A previously observed response of lettuce to high levels of IAA in aerial tissues [41] possibly indicates _G. diaz_ contributions to the plant available IAA.