## 3 Results and Discussion
### Growth Experiments with Fertilizer Addition through DoE  
With the aims of finding an optimal LED lights combination, balancing the number of hyper red and deep blue LED lights, that is capable of enhancing all the growth parameters, and investigating the possible effects in combination with fertilizer, a new experimental set-up was managed through an ad hoc DoE experimental plan. Table 4 shows the complete experimental plan and the obtained results, in which the average values of each response among three repetitions of the same experiment are indicated. As previously stated, with the aim to evaluate only fertilizer and LED lights effects, all the other parameters were kept as constant; thereafter, temperature and humidity were controlled during all the experiments to avoid environmental conditioning. Temperature and humidity were kept almost constant near 30 \({}^{\circ}\)C and 60% respectively, with restrained variation around 5% due to the employment of an indoor environment not perfectly conditioned. From a general observation of the results, germination occurred for almost all the basil seeds; in fact, only two of them did not germinate, and thereafter, the number is not statistically relevant. In addition, it must be noted that all the cultivation conditions applied according to this experiment plan were proved to be appropriate for basil, as it was confirmed by the absence of morphological and developmental abnormalities during plant growth. Observing only the data in Table 4, a general comparison can be stated with the results obtained without fertilizer, as shown in Table 5. From this comparison, it is clear that the fertilizer addition, by soil or by controlled-release fertilizer addition, is capable of improving the basil growth performances. In particular, it can be observed that plant height is always greater with fertilizer as well as the NoL and SLA parameters. Figures 5-7 show examples of the plants obtained at the end of the experimentation, respectively those grown under 3 HR:1 DB, 1 HR:1 DB, and 1 HR:3 DB, thereafter moving from a higher to lower proportion of hyper red LED light in relation to deep blue. As can be seen observing Figures 5-7 and the data in Table 4, the introduction of NPK controlled-release fertilizer has a positive effect on the plants' growth by increasing a considerable number of plants parameters (such as Height, TFM, TDM, LAI, and SLA), and in general, this effect is not influenced by the type of LED light. Nevertheless, from Figure 7, it appears clear that a more distinguishable difference among plants with and without NPK is appreciable, suggesting a possible synerge effect between NPK addition and 1 HR:3 DB LED lights combination that is capable of possibly promoting plant height and TFM. For these reasons, it is essential to study the ANOVA analysis to mathematically identify the possible correlation among NPK and LED lights combination as a function of the different measured parameters. Figure 5: Basil plants obtained under 3 HR:1 DB LED lights. The normal distribution of the residuals, as well as their homogeneity, has been analyzed (data not reported) for each response, confirming that the mathematical models derived can be used to explore the region of interest. The resulting models allowed describing the relationships between growth condition and the measured responses. The ANOVA results have been presented in Tables 6 and 7, where the quantification of the significance of factors and their interactions were reported as well as the fitting quality parameters as well as the effect sizes for each significant model. An inverse square root transformation was required to normalize the data and codify the hierarchy of the factors for some responses. The model correlating the factors (in single or interaction) to the panel data evaluation is significant, as confirmed by the \(p\)-value < 0.0001 for all the responses, which means that the probability of the data variation due to unknown factors is statistically irrelevant.