## 3 Results and Discussion
### Effect of Growing Medium on the Growth and Yield
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{\(\mathbf{C\times GM\)}}} & \multicolumn{3}{c}{**Leaves**} & \multicolumn{3}{c}{**Plant Height**} & \multicolumn{3}{c}{**Root**} & \multicolumn{3}{c}{**Stem**} & \multicolumn{3}{c}{**Leaves**} \\  & \multicolumn{3}{c}{**(n\({}^{\circ}\))**} & \multicolumn{3}{c}{**(cm)**} & & \multicolumn{3}{c}{**(mg d.w.)**} & & \multicolumn{3}{c}{**(mg d.w.)**} & & \multicolumn{3}{c}{**(mg d.w.)**} \\ \hline IMP \(\times\) TC & 5.0 \(\pm\) & 0.6 & e & 7.8 \(\pm\) & 1.1 & f & 34.0 \(\pm\) & 4.1 & c & 13.5 \(\pm\) & 1.3 & e & 111 \(\pm\) & 13 & c \\ IMP \(\times\) C1-60 & 6.1 \(\pm\) & 0.8 & a & 9.1 \(\pm\) & 0.8 & cd & 46.2 \(\pm\) & 8.6 & bc & 20.1 \(\pm\) & 1.2 & cde & 170 \(\pm\) & 18 & ab \\ IMP \(\times\) C1-30 & 4.9 \(\pm\) & 0.9 & e & 8.2 \(\pm\) & 0.9 & f & 30.9 \(\pm\) & 4.3 & c & 17.1 \(\pm\) & 0.9 & de & 128 \(\pm\) & 6.5 & bc \\ IMP \(\times\) C2-60 & 5.5 \(\pm\) & 0.5 & bcd & 9.1 \(\pm\) & 0.7 & cd & 54.4 \(\pm\) & 3.5 & abc & 19.5 \(\pm\) & 0.1 & cde & 141 \(\pm\) & 23 & bc \\ IMP \(\times\) C2-30 & 5.5 \(\pm\) & 0.8 & bcd & 8.1 \(\pm\) & 0.7 & f & 36.4 \(As in the surveys at 33 and 43 days after sowing, IMP lettuce showed no statistically significant differences in root, stem, and dry weight in dependence by substrates. Instead, at 54 days IMP \(\times\) C1-60 gave a greater leaf dry matter statistically significant than IMP \(\times\) TC. For VDI among the compost-based substrates, the best was C2-30. VDI \(\times\) C2-30 showed higher leaf dry matter values than the control (VDI \(\times\) TC). Compost has been shown to improve the amount of nutrients available to plants and enhance their growth with increased dry weight of both shoots and roots [65; 66; 67]. According to [PERSON] et al. [68], compost, over time, is a source of nutrients that are absorbed by plant roots [69], and its beneficial effect on yield is probably related to auxin-like molecules from the humic fraction. Similar to our results, [PERSON] et al. [70] found that in hydroponic lettuce (_Lactuca sativa_ var. Tanius) cultivation waste-based compost (from fruits, and vegetable and olive pruning) substrate significantly increased leaf dry weight (19.8%) of the plants compared to the conventional organic growing media constituents (cocodust). [PERSON] et al. [15] reported that compost produced from crop waste of vegetable green leaf utilized as a component of substrate to baby leaf species cultivation increased the dry weight of both shoot and root compared to the peat substrate. For lettuce (_Lactuca sativa_ var. Batavia verde Falstaff), the increase in dry weight was only observed for the roots at the lowest dose (C25). These different results could be due to differences in feedstocks, the transformation process, and the characteristics of the compost and its mixing ratios that influence the properties of the growing media. In addition, environmental conditions and cultivar-specific responses could be taken into account [67; 71]. Concerning the latter, our findings on dry matter accumulation at the three surveys conducted at 33, 43, and 54 DAS, indicated varietal-specific behavior of the lettuce cultivars with respect to the growth medium. At 33 and 43 DAS, the compost-containing growing media gave comparable results to the control in IMP lettuce plants; at harvest, C1-60 showed leaf dry weight even greater than the control. Instead, for VDI, already at 33 days after sowing, some compost-based growing media (C2-30, C2-60) gave higher dry matter values than the control. As for yield, the VDI cultivar resulted in more productivity than IMP (2.6 vs. 1.8 kg f.w. m\({}^{-2}\)). The varieties responded differently to the growing medium: the IMP variety showed the highest production values C1-60 (2.4 kg f.w. m\({}^{-2}\)) as did the VDI with C2-30 growing medium (3.2 kg f.w. m\({}^{-2}\)) (Figure 2).